McClements attended the National Institute of Dramatic Art (NIDA), graduating in 1985, alongside Baz Luhrmann, Sonia Todd and Justin Monjo. In 1988, McClements, along with a number of other people including Baz Luhrmann, set up an experimental theatre ensemble called 'Six Years Old', and they worked on expanding the play Strictly Ballroom, which was first produced in their second year of NIDA in 1984.
McClements is best known for her starring role as Rachel Goldstein on the Australian police drama Water Rats from 1996 to 1999. She had a recurring guest role on The Secret Life of Us in 2001, for which she won the AFI Award for Best Actress in a Guest Role in a Television Drama. She later starred as Rosie in the 2003 drama series CrashBurn and appeared in the Network Ten telemovie Mary Bryant in 2005. In 1993 she had a role in The Girl from Tomorrow Part II: Tomorrow's End.
Her latest television roles include Inspector/Superintendent Kerry Vincent, in the Australian police drama, Rush, and psychologist Christine Williams in the Showcase drama, Tangle. A second and third season of Tangle and Rush respectively were announced in 2009, and both aired in 2010. Tangle and Rush have been commissioned for new seasons, both to start filming in mid-2011. In 2010, McClements won an AFI award for her role in Tangle. She has also won ASTRA awards for her role in Tangle in 2011 and 2013.
McClements is also an accomplished stage actress, who has appeared in stage productions for many theatre companies, including Belvoir St Theatre, the Melbourne Theatre Company, the Sydney Theatre Company, Bell Shakespeare and the Malthouse Theatre. In 1987, McClements worked in Adelaide with the South Australia Theatre Company.
In 2011, McClements guest starred in a YouTube and Facebook only show called Queer as F**k, playing Mel – a friend of main character Aaron (Gary Abrahams).
In 2012, McClements was cast as Meg Jackson in Wentworth, a contemporary reimaginint of the Australian classic Prisoner. She was cast in a leading role for Season One of Wentworth, and her character did not appear beyond episode one. Also in 2013, McClements will return to the stage, in Sharr White's play The Other Place, for the Melbourne Theatre Company, and Phèdre for Bell Shakespeare.
Earlier in 2013, McClements was cast in new ABC telemovie The Broken Shore, alongside Don Hany, Dan Wyllie and Claudia Karvan. It will premiere at the Adelaide Film Festival in October 2013, and air on the ABC in early 2014.
In September 2013, McClements was cast in the film The Menkoff Method, which will be directed by David Parker.
McClements' partner is actor Jacek Koman who also guest starred in The Secret Life of Us as Dominic, though they were not on the show at the same time. They met at the Anthill Theatre in Melbourne in the late 1980s, and have a daughter named Coco (born July 2001) and a son named Quincy (born May 2007). Her sister is Georgina McClements, a producer, who has credits in shows such as Summer Heights High and Real Stories. Her brother is Brendan McClements, who is the current CEO of Victorian Major Events Company. McClements is good friends with fellow actress Claudia Karvan, whom she met at the AFI awards in 1990 and starred with in the film Redheads in 1992.