Bird allowed outside tavern (6)
I believe the answer is:
linnet
'bird' is the definition.
(linnet is a kind of bird)
'allowed outside tavern' is the wordplay.
'allowed' becomes 'let' (to let is to allow or permit).
'outside' indicates putting letters inside (some letters go outside others).
'tavern' becomes 'inn' (I've seen this before).
'let' going around 'inn' is 'LINNET'.
(Other definitions for linnet that I've seen before include "North London terminus" , "Member of finch family" , "Songbird (to 6 18)" , "Brown-grey kind of finch" , "Brown-grey species of finch" .)