Make a mistake feeding rustic poet (7)
I believe the answer is:
herrick
'poet' is the definition.
(I know that Herrick is a poet)
'make a mistake feeding rustic' is the wordplay.
'make a mistake' becomes 'err' (to err is to make an error).
'feeding' means one lot of letters goes inside another (one word is fed by another set of letters).
'rustic' becomes 'hick' (synonyms).
'err' inserted within 'hick' is 'HERRICK'.
(Other definitions for herrick that I've seen before include "Robert --, English poet" , "Gather ye rosebuds poet" , "Lyric poet" .)