Born in Bellshill, Lanarkshire, he was part of the Celtic team that won the European Cup in 1967. Clark is perhaps the most unheralded player among the Lisbon Lions team. His undramatic style of team play in sweeping up beside fellow centre back, Billy McNeil, was integral to the success of the team. His role as Celtic's sweeper earned him the nickname "The Brush."
Clark earned four caps for Scotland all in his time with Celtic.
He left Celtic for Morton in 1971, where he retired two years later from playing.