Poetic "soon" (4)
I believe the answer is:
anon
'poetic soon' 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 "In a little while (informal)" , "Immediately" , "Soon; unattributed" , "Without known author" , "Of unknown name (abbr)" .)