As a senior in 1979, he was moved to strong safety and received Black College All-American honors.
[1] Clinkscale was signed as an undrafted free agent by the Dallas Cowboys after the 1980 NFL draft.
As a rookie, he appeared in all 16 games, playing on passing downs to help fill the void left by Cliff Harris' retirement and an injured Randy Hughes.
In 1981, he entered training camp competing with Benny Barnes for the starting strong safety position that was left open with the retirement of Charlie Waters, but missed the entire season due to an Achilles tendon injury he suffered in training camp.
[3] That year, he was a part of a secondary that earned the nickname "Thurman's Thieves", because of the amount of big plays and turnovers they generated.
[4] In 1986, he was released 5 games into the season and his position was assigned to Bill Bates, after staging a holdout from the start of training camp.
In 1986, Clinkscale was claimed off waivers by the Indianapolis Colts, but he did not agree to a contract and had to be signed as a free agent until October 29.