Born in Liverpool, the oldest of four children born to Karen (née Sullivan) and Geoffrey Thomas Clancy, Clancy formed girl band Genie Queen, who were managed by Andy McCluskey from Orchestral Manoeuvres in the Dark (OMD).
In summer 2006, the second cycle of Living TV's Britain's Next Top Model included Clancy as one of the thirteen finalists in the competition, competing over 10 weeks for a modelling contract. Clancy made it to the final runway show with fellow contestant Lianna Fowler, eventually becoming the runner up.
After appearing on Britain's Next Top Model, Clancy modelled for several magazines and newspapers. In May 2007, Clancy appeared on the cover of Arena magazine, and modelled the Triumph Bonneville Motorbike in the Daily Mail newspaper. Clancy was chosen to appear in Sports Illustrated magazine in the 2010 swimsuit edition. Clancy was featured for her sporting connection to Peter Crouch and was photographed for the magazine wearing only body paint to make it appear as if she was wearing an England shirt.
Clancy appeared in a 2010 campaign for Umbro sportswear, modelling an England shirt, along with other footballer's wives and girlfriends from countries that have won the World Cup. Clancy walked in the Giles Deacon Ready-To-Wear line Giles Spring 2011 collection.
In March 2011 Clancy appeared on the Elite Model Management: New York division website. In July 2013, she appeared as part of London designer Hasan Hejazi's campaign, in a fashion editorial by Absynth Photographic and a fashion film by Gabriel Gettman. Clancy also modelled for the August 2011 cover of UK Esquire shot by photographer Sølve Sundsbø.
In December 2013 Clancy was featured in LOVE magazine's Advent Calendar alongside Suki Waterhouse and Cara Delevingne.
In July 2014, Clancy appeared on the cover of British Marie Claire and in March 2015, British Elle.
Clancy has appeared as a talking head in the documentaries Slave to Fashion and The Ultimate Bikini Guide for Channel 4, as a guest on programmes such as Richard & Judy, The Chris Moyles Show, Friday Night with Jonathan Ross, GMTV, This Morning and in her own reality TV series Abbey and Janice: Beauty and the Best which followed her attempts to break the Los Angeles modelling scene with Janice Dickinson as her mentor. The show aired from 14 May to 18 June 2007 on Living TV.
Clancy featured in the third series of Hell's Kitchen. She was the third contestant to be voted off the show by the public, and the fifth to leave overall.
On 10 May 2009, Clancy featured on Chris Moyles' Quiz Night alongside Patsy Kensit. She won her episode and was the overall winner of the first series.
Clancy also co-hosted the ITV2 series, The Fashion Show with model Michelle de Swarte and George Lamb. Her cousin Chloe Cummings, made the top 13 contestants in the fifth cycle of Britain's Next Top Model, of which Clancy herself was a guest in episode 8, being the first ex-contestant from the Top Model franchise to appear on the judging panel.
On 22 December 2009, Clancy appeared as a "contestant" on a spoof version of Blind Date as part of an episode of Alan Carr: Chatty Man in which Cilla Black was a guest.
In April 2010, Clancy was featured in ITV2's The Parent Trip along with her mother Karen. She also appeared as a panellist on A League Of Their Own.
Clancy was a regular guest on James Corden's World Cup Live.
She also co-hosted the reality TV show Great British Hairdresser in 2011.
In 2013, Clancy won the eleventh series of Strictly Come Dancing. Her professional partner was newcomer and Burn the Floor dancer, Aljaž Skorjanec. On 16 November 2013, they received their first "10s" of the competition, during Blackpool Week. On 30 November 2013, they became the first couple that year to score a perfect "40", during Musicals Week.
In 2015, Clancy was announced as the new host for a revived series of Britain's Next Top Model, 9 years after she began her own career on the show.
In March 2016, Clancy's first book, "Remember My Name", was published.
Clancy was ranked 37th in FHM magazine's annual 100 sexiest women in the world poll of 2007 but dropped down to number 55 the following year. In 2009, Clancy had moved up to 12th place, and in 2010 she went up to 10th place in the annual poll.
In July 2012 The Sun Newspaper announced Clancy as their exclusive Beauty Columnist writer. Clancy was the subject of widespread criticism in her home town of Liverpool, as the paper was boycotted in the city for printing false allegations against supporters of Liverpool football club in the aftermath of the Hillsborough disaster in 1989. Clancy later apologised for the column.
Clancy's brother Sean is a footballer who plays for A.F.C. Telford United. He was also a castmember of the short-lived E4 reality series Desperate Scousewives. Her other brother John is the lead singer and rhythm guitarist in the indie band JUDAS.
Clancy started dating footballer Peter Crouch in 2006. The couple were engaged from July 2009 and their daughter Sophia Ruby was born 14 March 2011. On 30 June 2011, Clancy and Crouch married at Stapleford Park Hotel in Leicestershire. Their second daughter Liberty Rose was born on 1 June 2015.