The Green Bay Packers chose Clark in the first round (fourth pick overall) of the 1980 NFL Draft, but refused to play for them. Clark then chose to play for the Toronto Argonauts of the CFL instead to avoid playing for Green Bay. After two years in Canada, he played for the NFL's New Orleans Saints for seven seasons from 1982 to 1988, and joined the Kansas City Chiefs for one final NFL season in 1989.
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.