Judge can rule if that is correct, initially (6)
I believe the answer is:
critic
'judge' is the definition.
(critic is a kind of judge)
'can rule if that is correct initially' is the wordplay.
'initially' indicates taking the first letters.
The initial letters of 'can rule if that is correct' is 'CRITIC'.
(Other definitions for critic that I've seen before include "Reviewer - fault-finder" , "I might rebuke" , "Reviewer of plays, films etc" , "Reviewer of others' work" , "Person who reviews plays, films etc" .)