She is known for portraying Faith Taylor on the soap opera Days of Our Lives (1989–1990), Julie Cooper on Fox's teen drama series The O.C.

[8] Clarke appeared on the daytime soap opera Days of Our Lives as Faith Taylor (where her father was a senior cast member), and starred in the television series Soldier of Fortune, Inc. (1997–1999).

She also guest-starred on Xena: Warrior Princess (1997) as the Amazon chieftain Velasca, Firefly (2003) the brothel madam Nandi, Charmed (2002) as the Siren, and has had six appearances on CSI (2001–2011) where she played dominatrix Lady Heather.

[9] She portrayed Julie Cooper in the teen drama series The O.C., that aired on the Fox network from August 5, 2003, to February 22, 2007, running a total of four seasons.

[10][11][12] Clarke's character Julie Cooper was often characterized as devious and selfish,[13] with USA Today calling her a "shallow vixen".

Clarke was originally billed as a guest star in the first few episodes in which she appeared, but due to fan response was offered a series regular contract.

Secondly, she commands every single room she walks into, whether it's in a pink Juicy Couture tracksuit or a groovy, off-the-shoulder top.

"[16] Clarke has appeared on HBO's comedy-drama series Entourage (2005–2011) as a fictionalized version of herself, married to Malcolm McDowell's character Terrance McQuewick.

[17][18] Clarke portrayed Blithe Meacham in the television film She Drives Me Crazy (2007), which was produced by Kelly Rowan.

In 2010, she appeared on The CW show The Vampire Diaries (2010–2017) as Kelly Donovan, a mother who discovers her daughter has died.