Prior to, in poetry (3)
I believe the answer is:
ere
'prior to in poetry' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ere that I've seen before include "Archaic word for before - a palindrome" , "Old prior" , "Before (lit.)" , "One who steals" , "Before (in poetry)" .)