Clarke appeared in the daytime soap opera Days of Our Lives (where her father John Clarke was a senior cast member), and starred on Soldier of Fortune, Inc. for both of its seasons. She also guest starred on Xena: Warrior Princess, Firefly, Charmed, and has had four appearances on CSI where she played the dominatrix, Lady Heather. She also appeared in the Seinfeld episode "The Muffin Tops", playing Jerry's girlfriend who likes anything hairless. Coincidentally, one of her appearances on CSI was with Kelly Rowan, who would later be her co-star on The O.C..

She appeared as a guest star on the FOX drama The O.C., and due to fan response was offered a contract for her role as Julie Cooper, a cunning socialite who marries for money. Clarke accepted the role and became an integral part of the show's storylines. As well as starring on The O.C., she has appeared on HBO's hit series Entourage as a fictionalized version of herself, married to Malcolm McDowell's Terrance McQuewick. Clark