Male swine (4)
I believe the answer is:
boar
'male swine' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for boar that I've seen before include "Sow's mate" , "Male swine" , "Wild swine" , "The head for drink Falstaff had" , "Resting place for birds or bats" .)