Soon, in poetry (4)
I believe the answer is:
anon
'soon in poetry' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for anon that I've seen before include "Nameless (abbr.); soon" , "coming after a call" , "Immediately" , "Incognito (abbrev)" , "Shortly; unknown" .)