I study old cinema, initially with ultimate critic (10)
I believe the answer is:
iconoclast
'critic' is the definition.
(I have seen 'Critic of faith' mean 'iconoclast' so perhaps 'critic' could also mean 'iconoclast')
'i study old cinema initially with ultimate' is the wordplay.
'study' becomes 'con' (con can mean to study).
'initially' says to take the initial letters.
'with' is a charade indicator (letters next to each other).
'ultimate' becomes 'last' (similar in meaning).
The first letters of 'old cinema' is 'oc'.
'i'+'con'+'oc'+'last'='ICONOCLAST'
(Other definitions for iconoclast that I've seen before include "heretic" , "Debunker of reputations" , "Challenging type" , "Critic of faith" , "A dissident" .)