Judge runs into a vicious dog, perhaps? (7)
I believe the answer is:
arbiter
'judge' is the definition.
(I know that arbiter is a type of judge)
'runs into a vicious dog perhaps?' is the wordplay.
'runs' becomes 'r' (cricket abbreviation).
'into' is an insertion indicator.
'vicious dog perhaps?' becomes 'biter' (I've seen this before).
'a'+'biter'='abiter'
'r' inserted into 'abiter' is 'ARBITER'.
(Other definitions for arbiter that I've seen before include "He'll decide" , "One must exercise judgment" , "Source of authority" , "Mediator or referee" , "One settling disputes" .)