Swine finds nothing in pub (4)
I believe the answer is:
boar
'swine' is the definition.
(male pig)
'nothing in pub' is the wordplay.
'nothing' becomes 'O' (looks like zero - 0).
'in' indicates putting letters inside.
'pub' becomes 'bar' (both are drinking establishments).
'o' placed into 'bar' is 'BOAR'.
'finds' is the link.
(Other definitions for boar that I've seen before include "Wild pig sounds tedious" , "Wild animal, sounds like drill" , "Uncastrated male pig" , "Wild swine" , "Sow's mate" .)