Probably his longest lasting role was that of Casey Junior in the syndicated 1957-1958 television series, Casey Jones, starring Alan Hale, Junior., in the title role, with supporting cast members Mary Lawrence as Mistress Jones, Dub Taylor as Fireman Wallie Sims, and Eddy Waller as "Red Rock", the train conductor. Clark appeared in the movies Invasion of the Body Snatchers, Ransom!, Gun Duel in Durango, Rebel in Town, The Happy Road, Bring Your Smile Along, and The Ten Commandments.
Clark made a guest appearance on Perry Mason as the title character in the 1958 episode, "The Case of the Pint-Sized Client." He also appeared in episodes of Alfred Hitchcock Presents, The Loretta Young Show, The Jimmy Durante Show, The Americans (a drama of the American Civil War), Lassie, General Electric Theater, Ford Theatre, Studio 57, The Pepsi-Cola Playhouse, Screen Directors Playhouse, Climax!, Front Row Center, Dick Powell"s Zane Grey Theater, Northwest Passage, Crossroads, Bachelor Father.
A son of Robert Boyd Clark and the former Jean Dahl, Clark began his professional career at the age of six when he was introduced to the accordion. He played in many public events, including United Service Organizations shows, professional wrestling matches, Kiwanis International, and the Benevolent and Protective Order of Elks.
In addition to his movie and television appearances, he performed at the Hollywood Bowl and at local festivals and events. Although Clark is semi-retired from show business he still makes an occasional public appearance.
One of his more recent was as a guest of the 2012 Memphis Film Festival"s "A Gathering of Guns 4: A television Western Reunion" at the Whispering Woods Hotel and Conference Center in Olive Branch, Mississippi.
In 2014 he portrayed Tharn in the fan produced Star Trek episode "Fairest of Them All".