Catch a bunker (4)
I believe the answer is:
trap
I believe this is a double definition.
'catch' is the first definition.
(trapping is a kind of catching)
'a bunker' is the second definition.
('trap' can be a synonym of 'bunker')
(Other definitions for trap that I've seen before include "Lock" , "Catch; two-wheeled carriage" , "It commonly has a role in speaking" , "Means of transport (sometime sprung!)" , "that may catch a speeding motorist" .)