After attending Trinidad State Junior College for two years, where he had a successful career, he became the first African-American varsity football player at the University of Colorado at Boulder, joining the Buffaloes in September 1954.
He was joined by John Wooten the following year and because this was before the civil rights movement, the pair often had to endure open racism outside of Boulder.
[1] As a junior, he was an honorable-mention All-Big 7 conference performer, when he was second in the league with 407 receiving yards, during a run-oriented era.
Trailing 13–0 against the University of Missouri and needing a tie or a win to clinch a berth for the 1957 Orange Bowl, Clarke scored 2 second half touchdowns.
Clemson University originally stated that they would not play in the bowl against a team with black athletes, but later changed its position and would end up losing 27–21.
He had a total of 10 catches during those three years at offensive right end and was left unprotected in the 1960 NFL Expansion Draft.
The coach appreciated his speed, soft hands and his ability to run precise routes, so he was converted into a split end.
Mostly a backup behind Billy Howton and Fred Dugan, he appeared in 8 games (3 starts), registering 9 receptions, 290 yards, 3 touchdowns and a 32.2-yard average.
Additionally, he began a streak of seven consecutive games with at least a touchdown reception, which still stands as a Cowboys record shared with Bob Hayes (1965–1966), Terrell Owens (2007), and Dez Bryant (2012).
[5] On September 23, Clarke was part of an infamous play where, for the first time in an NFL game, points were awarded for a penalty.
The Cowboys were holding in the end zone on a 99-yard touchdown pass from Eddie LeBaron to Clarke, and the Pittsburgh Steelers were awarded a safety, helping them win the game 30–28.