Door fastener in confessional at church (5)
I believe the answer is:
latch
'door fastener' is the definition.
(I've seen this before)
'in confessional at church' is the wordplay.
'in' says the answer is hidden in the clue.
'LATCH' is hidden within 'confessional at church'.
(Other definitions for latch that I've seen before include "retainer" , "Gate fastening" , "Gate bar" , "Door securer" , "Small bar for fastening a door" .)