Slander girl in drinking establishment (7)
I believe the answer is:
besmear
'slander' is the definition.
(smear can mean to slander)
'girl in drinking establishment' is the wordplay.
'girl' becomes 'esme' ().
'in' means one lot of letters goes inside another.
'drinking establishment' becomes 'bar' (I've seen this before).
'esme' put inside 'bar' is 'BESMEAR'.
(Other definitions for besmear that I've seen before include "Cover with (something)" , "Bedaub; pollute" , "Sully" .)