Rum pie served up for the referee (6)
I believe the answer is:
umpire
'the referee' is the definition.
(I've seen this before)
'rum pie served up' is the wordplay.
'served up' indicates an anagram.
'rum'+'pie'='rumpie'
'rumpie' anagrammed gives 'UMPIRE'.
'for' is the link.
(Other definitions for umpire that I've seen before include "A field judge in circket" , "Impure (anag) - adjudicator" , "Football official" , "Kind of referee as in cricket" , "The ref in cricket match" .)