Fergie (United's ultimate character): "Corrupt ref shocks you" (7,2,4)
I believe the answer is:
duchess of york
'fergie' is the definition.
(nickname of Sarah Ferguson, Duchess of York)
'united's ultimate character corrupt ref shocks you' is the wordplay.
'ultimate character' indicates one should take the final letters (ultimate can mean last).
'corrupt' indicates an anagram.
The last letter of 'united' is 'd'.
'ref'+'shocks'+'you'='refshocksyou'
'refshocksyou' is an anagram of 'uchessofyork'.
'd'+'uchessofyork'='DUCHESS OF YORK'
(Another definition for duchess of york that I've seen is " Mother of kings".)