Drug that's acceptable in church? (4)
I believe the answer is:
coke
'drug' is the definition.
(cocaine)
'acceptable in church?' is the wordplay.
'acceptable' becomes 'ok' (OK can mean acceptable or fine).
'in' means one lot of letters goes inside another.
'church?' becomes 'CE' (abbreviation for Church of England).
'ok' put inside 'ce' is 'COKE'.
'that's' is the link.
(Other definitions for coke that I've seen before include "Nose candy" , "Fuel derived from coal" , "Drug (abbr) - soft drink (abbr)" , "'Soft drink and hard drug, in short (4)'" , "Furnace fuel" .)