Bird in pub now large (4,3)
I believe the answer is:
barn owl
'bird' is the definition.
(barn owl is a kind of bird)
'pub now large' is the wordplay.
'pub' becomes 'bar' (both are drinking establishments).
'large' becomes 'L' (eg in clothes sizes).
'bar'+'now'+'l'='BARN OWL'
'in' acts as a link.
(Other definitions for barn owl that I've seen before include "Mottled buff and white night bird" , "Nocturnal raptor" , "Endangered night bird" , "Flier" , "Night-flying raptor" .)