Wild pig hidden in cupboard (4)
I believe the answer is:
boar
'wild pig' is the definition.
(I've seen this in another clue)
'hidden in cupboard' is the wordplay.
'hidden in' indicates the answer is hidden within the clue.
'BOAR' is hidden in the letters of 'cupboard'.
(Other definitions for boar that I've seen before include "Resting place for birds or bats" , "Sow's mate" , "Male swine" , "A wild male pig" , "Uncastrated male pig" .)