Funfair turns out to be rough (7)
I believe the answer is:
ruffian
'be rough' is the definition.
(thesaurus)
'funfair turns out' is the wordplay.
'turns out' indicates an anagram.
'funfair' is an anagram of 'RUFFIAN'.
'to' is the link.
(Other definitions for ruffian that I've seen before include "Funfair (anag)" , "Yobbo" , "Lout" , "Thug" , "Hoodlum" .)