Wearing #16, Clarke made his NHL debut on October 11, 1969, against the Minnesota North Stars. He recorded his first point on October 22 against the Toronto Maple Leafs, an assist on Lew Morrison's 3rd period goal, and he scored his first goal on October 30 against the New York Rangers, beating Rangers goaltender Ed Giacomin 16:36 into the 3rd period. Clarke played the entire 76-game schedule his rookie season and recorded 46 points (15 goals, 31 assists) while earning a trip to the NHL All-Star Game.
Wearing #16, Clarke made his NHL debut on October 11, 1969, against the Minnesota North Stars. He achieved his initial feat on October 22 against the Toronto Maple Leafs, providing an assist in Lew Morrison's 3rd period goal, and he scored his first objective on October 30 against the New York Rangers, defeating Rangers goaltender Ed Giacomin 16:36 into the 3rd period. Clarke played every game of his rookie season and recorded 46 points (15 goals, 31 assists) while earning a trip to the NHL All-Star Game.