Sporting god secured by the rack, or somehow enslaved? (8)
I believe the answer is:
olympian
'sporting god' is the definition.
(an Olympic athlete)
I don't understand the rest of the clue.
(Other definitions for olympian that I've seen before include "Competitor in games held every four years" , "Top athlete" , "Relating to the home of the Greek gods" , "Majestic" , "Contestant in revival of ancient games" .)