Allow outside pub to see bird (6)
I believe the answer is:
linnet
'bird' is the definition.
(linnet is a kind of bird)
'allow outside pub' is the wordplay.
'allow' becomes 'let' ('let' can be a synonym of 'allow').
'outside' is an insertion indicator.
'pub' becomes 'inn' (I've seen this before).
'let' going around 'inn' is 'LINNET'.
'to see' acts as a link.
(Other definitions for linnet that I've seen before include "North London terminus" , "Type of finch" , "Finch so named because it feeds on flax" , "Finch formerly popular as a pet" , "Brown-grey kind of finch" .)