Paint to be treated in a church? If need be (2,1,5)
I believe the answer is:
at a pinch
'if need be' is the definition.
(at a pinch means if required)
'paint to be treated in a church?' is the wordplay.
'to be treated' indicates an anagram.
'in' indicates putting letters inside.
'church?' becomes 'ch' (common abbreviation).
'paint' anagrammed gives 'tapin'.
'a'+'ch'='ach'
'tapin' placed into 'ach' is 'AT A PINCH'.
(Other definitions for at a pinch that I've seen before include "if need be" , "In case of necessity" , "If absolutely necessary" , "In time of difficulty or necessity - nip it" , "in case of emergency" .)