Singer allowed to entertain pub (6)
I believe the answer is:
linnet
'singer' is the definition.
(I know that linnet is a type of singer)
'allowed to entertain pub' is the wordplay.
'allowed to' becomes 'let' (to let something happen is to allow it).
'entertain' is an insertion indicator.
'pub' becomes 'inn' (an inn is a type of pub).
'let' going around 'inn' is 'LINNET'.
(Other definitions for linnet that I've seen before include "North London terminus" , "A singing bird as from Yeats's Innisfree" , "Brown-gray kind of finch" , "Common finch" , "A British finch" .)