Kind of door catch (4)
I believe the answer is:
trap
I believe this is a double definition.
'kind of door' is the first definition.
(I've seen this in another clue)
'catch' is the second definition.
(I know that catch is a is a more specific form of the action of trap)
(Other definitions for trap that I've seen before include "Light carriage - it's sometimes sprung!" , "Part of a snare" , "Device to catch prey" , "Means of transport - sometimes sprung!" , "Cakehole (slang)" .)