Cry about donkey in drinking bout (7)
I believe the answer is:
wassail
'drinking bout' is the definition.
(thesaurus)
'cry about donkey in' is the wordplay.
'cry' becomes 'wail' (wailing is a kind of crying).
'about' is a reversal indicator.
'donkey' becomes 'ass' (ass is a term for a donkey).
'in' indicates putting letters inside.
'ass' written backwards gives 'ssa'.
'wail' going around 'ssa' is 'WASSAIL'.
(Other definitions for wassail that I've seen before include "festive drink" , "celebration" , "Lively festivities; spiced ale" , "Sing Christmas carols" , "Go carol-singing" .)