 Clemenson began his career in a number of character roles in film and television.He was a law student in the television version of "The Paper Chase", Alex Keaton's English teacher in the television show "Family Ties", a security salesman on "The Golden Girls", a suspect in season 10, episode 14 of "NYPD Blue", a bailiff in the Ivan Reitman movie "Legal Eagles", a flight surgeon in the movie "Apollo 13", a cop in "The Big Lebowski", a killer in "The Fisher King", and Dr. Dale Lawrence in the movie "And the Band Played On".He had a regular role as Socrates Poole, a lawyer in the Old West, in the Fox series "The Adventures of Brisco County, Jr."

In 1999, Clemenson appeared in the "Buffy the Vampire Slayer" episode "Bad Girls" as a grotesquely obese demon named Balthazar.