Judge's a right attack dog, perhaps (7)
I believe the answer is:
arbiter
'judge's' is the definition.
(thesaurus)
'a right attack dog perhaps' is the wordplay.
'a right' becomes 'ar' (I've seen this in other clues).
'attack dog perhaps' becomes 'biter'.
'ar'+'biter'='ARBITER'
(Other definitions for arbiter that I've seen before include "Source of authority" , "One appointed to settle a dispute" , "Rear bit (anag.)" , "Settler of dispute" , "One decides in disputes" .)