Clarke, who is on the Class A Dayton roster, will begin serving his suspension at the start of next season.
The 22-year-old left-hander was a 19th-round pick by the Reds in the 2009 First-Year Player Draft, out of Ontario, Canada. He pitched in only one game this season, on June 24, for the Reds' rookie affiliate in Arizona. Last season, he was 4-3 with a 3.06 ERA in 14 games split between Dayton and rookie league Billings.
Andrew Simon is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.