Happen to put on judge's wig (6)
I believe the answer is:
berate
'wig' is the definition.
(thesaurus)
'happen to put on judge's' is the wordplay.
'happen' becomes 'be' (I've seen this in another clue).
'to put on' says to put letters next to each other.
'judge' becomes 'rate' (rating is a kind of judging).
'be'+'rate'='BERATE'
(Other definitions for berate that I've seen before include "Scold or chide severely" , "Condemn" , "Carpet" , "slate" , "Censure severely or angrily" .)