Clark won five tournaments in the 1951 season, including the singles title in Monte Carlo in 1951 after a five-set win in the final against compatriot Fred Kovaleski.

That same year he defeated Whitney Reed to reach the final of the Pennsylvania State tennis championship, only to fall to future Hall of Famer Vic Seixas.

[6] In 1954, he won the singles title at the tournament in Cincinnati Masters, defeating Sammy Giammalva, Sr., in the final in three straight sets.

He reached the final at the Newport Casino Invitational in 1954, only to lose to Ham Richardson in five sets, in a match that lasted more than four hours.

They reached the finals of the U.S. Clay Court Championship, and the semifinals of the U.S. Nationals, upsetting the team of future International Hall of Famers Ken Rosewall and Lew Hoad in the quarterfinals.