Rarebit cooked up for the referee (7)
I believe the answer is:
arbiter
'the referee' is the definition.
(thesaurus)
'rarebit cooked up' is the wordplay.
'cooked up' indicates an anagram.
'rarebit' anagrammed gives 'ARBITER'.
'for' acts as a link.
(Other definitions for arbiter that I've seen before include "One who settles disputes" , "Judge - mediator" , "One must exercise judgment" , "Ref" , "Referee or judge of rarebit" .)