Catholic wants to overhaul beliefs (5)
I believe the answer is:
credo
'beliefs' is the definition.
(I've seen this before)
'catholic wants to overhaul' is the wordplay.
'catholic' becomes 'C' (abbreviation as in RC for Roman Catholic).
'wants' is a charade indicator (letters next to each other).
'to overhaul' becomes 'redo' (I've seen this in another clue).
'c'+'redo'='CREDO'
(Other definitions for credo that I've seen before include "Doctrine or belief" , "System of principles" , "Set of beliefs about leftist circle" , "Belief system" , "Dogma" .)