Church work must be cut (4)
I believe the answer is:
chop
'cut' is the definition.
(chop is a kind of cut)
'church work' is the wordplay.
'church' becomes 'ch' (common abbreviation).
'work' becomes 'op' (abbreviation for opus).
'ch'+'op'='CHOP'
'must be' acts as a link.
(Other definitions for chop that I've seen before include "Cut; slice of meat" , "Thick slice of meat, often with rib" , "Cut of meat; hack" , "Abolish, cut of meat" , "Cutlet" .)