Judge a right vicious dog? (7)
I believe the answer is:
arbiter
'judge' is the definition.
(I know that arbiter is a type of judge)
'a right vicious dog?' is the wordplay.
'a right' becomes 'ar' (I've seen this in other clues).
'vicious dog?' becomes 'biter' (I've seen this in another clue).
'ar'+'biter'='ARBITER'
(Other definitions for arbiter that I've seen before include "Ref" , "Judge, final authority" , "Decision maker" , "Judge - mediator" , "One has the authority to settle disputes" .)