Before signing with Washington in 1955, Clarke pitched in the Negro leagues, including service with the Cleveland Buckeyes and Memphis Red Sox.

In his first season in the Senators' system, Clarke compiled a win–loss record of 16–12 in 33 games (32 as a starting pitcher), with an earned run average of 3.40 in 262 innings pitched for the Charlotte Hornets of the Class A Sally League.

The Senators' relief pitchers, Chuck Stobbs and Pedro Ramos, then gave up the tying runs and ultimately lost the game, 8–6.

[1] Clarke's seventh and last MLB game, September 24 against the Orioles, was his finest: appearing in relief, he set down all nine Baltimore batters he faced over three innings.

[2] During his MLB trial, Clarke allowed 17 hits, 11 earned runs and 14 walks in 21+1⁄3 innings pitched, with nine strikeouts, no decisions to his record and an ERA of 4.64.