Cold tea knocked back outside pub for entertainment (7)
I believe the answer is:
cabaret
'for entertainment' is the definition.
(cabaret is a kind of entertainment)
'cold tea knocked back outside pub' is the wordplay.
'cold' becomes 'C' (eg on taps).
'knocked back' is a reversal indicator.
'outside' is an insertion indicator (some letters go outside others).
'pub' becomes 'bar' (both are drinking establishments).
'tea' reversed gives 'aet'.
'aet' going around 'bar' is 'abaret'.
'c'+'abaret'='CABARET'
(Other definitions for cabaret that I've seen before include "Floor-show as in nightclub" , "goes on in nightclub?" , "Entertainment at night club" , "Entertainment at restaurant" , "Evening entertainment as in nightclub" .)