Vilifier’s part of speech about feeding wild creatures (9)
I believe the answer is:
denouncer
'vilifier's' is the definition.
(someone who denounces or vilifies)
'part of speech about feeding wild creatures' is the wordplay.
'part of speech' becomes 'noun' (noun is a part of speech).
'about' becomes 'c' (circa).
'feeding' is an insertion indicator (one word is fed by another set of letters).
'wild creatures' becomes 'deer' (deer are wild creatures).
'noun'+'c'='nounc'
'nounc' put inside 'deer' is 'DENOUNCER'.
(Other definitions for denouncer that I've seen before include "One making a public accusation" , "One condemns" , "Informer against" , "Castigator" .)