Head of church inclined to accept saint's purification (9)
I believe the answer is:
cleansing
'purification' is the definition.
(I know that purification can be written as cleansing)
'head of church inclined to accept saint's' is the wordplay.
'head of' says to take the initial letters.
'inclined' becomes 'leaning' (similar in meaning).
'to accept' is an insertion indicator.
'saint' becomes 's'.
The initial letter of 'church' is 'c'.
'leaning' going around 's' is 'leansing'.
'c'+'leansing'='CLEANSING'
(Other definitions for cleansing that I've seen before include "Nice slang for making thoroughly free from dirt (9)" , "Purging" .)