The Green Bay Packers selected Clark in the first round (fourth pick overall) of the 1980 NFL Draft, but he refused to play for them, and instead joined the Toronto Argonauts of the CFL. After two years in Canada, he played for the NFL's New Orleans Saints for seven seasons from 1982 to 1988, and then played for the Kansas City Chiefs in 1989, his final NFL season.
He later played a single season for the World League of American Football's Barcelona Dragons. Clark was drafted in the first round of the supplemental draft by the Barcelona Dragons in 1991. His experience and leadership were key to the Dragons successful first season. Clark started all ten games and was co-leader in sacks with seven that season.