Relating to four-yearly games (7)
I believe the answer is:
olympic
'relating to four-yearly games' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for olympic that I've seen before include "having reached peak in sporting excellence" , "Of a worldwide sporting movement" , "Of Summer or Winter games" , "It may precede record" , "Of ancient Greek site (of original games)" .)