Clark was on the Lions' roster during training camp and was let go during the final round of roster cuts. He signed with the UFL's Florida Tuskers in November of last year. After going to the UFL championship with the Tuskers (they lost to the Las Vegas Locos for the second consecutive year), he ended up back on the Lions' roster in December.
Clark was set to become a restricted free agent this offseason. Twentyman reports that the Lions had interest in bringing him back, but that won't be possible now that Clark has opted to retire at the age of 27.