Compose an awful polemic (7)
I believe the answer is:
compile
'compose' is the definition.
(I know that compose can be written as compile)
'an awful polemic' is the wordplay.
'an awful' indicates an anagram.
'polemic' is an anagram of 'COMPILE'.
(Other definitions for compile that I've seen before include "Assemble (a collection)" , "Put together" , "Marshal" , "Polemic (anag.)" .)