Knock back poet whose work is taking off? (8)
I believe the answer is:
parodist
'whose work is taking off?' is the definition.
(take off can mean to mock or parody)
'knock back poet' is the wordplay.
'knock' becomes 'rap' (synonyms).
'back' says the letters should be written backwards.
'poet' becomes 'odist' (someone writing odes).
'rap' reversed gives 'par'.
'par'+'odist'='PARODIST'
(Other definitions for parodist that I've seen before include "One takes off" , "The caricaturist" , "One makes fun" , "He sends up" , "Comic imitator" .)