Cheer, say, with drink getting knocked back (3,2)
I believe the answer is:
egg on
'cheer' is the definition.
(thesaurus)
'say with drink getting knocked back' is the wordplay.
'say' becomes 'eg'.
'with' is a charade indicator (letters next to each other).
'drink' becomes 'nog' (nog is a kind of drink).
'getting knocked back' says the letters should be written backwards.
'nog' backwards is 'gon'.
'eg'+'gon'='EGG ON'
(Other definitions for egg on that I've seen before include "Urge, impel" , "Incite, encourage" , "Encourage (someone to do a risky thing)" , "Fire" , "Prompt" .)