Hinged fastener (4)
I believe the answer is:
hasp
'hinged fastener' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for hasp that I've seen before include "Hinged metal fastener" , "part of a lock" , "Door latch" , "Fastening plate, clasp" , "Hinged fastening" .)