Relating to four-yearly games (7)
I believe the answer is:
olympic
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">relating to four-yearly games</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(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)" .)