Frequently, in verse (3)
I believe the answer is:
oft
'frequently in verse' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for oft that I've seen before include "''... in the stilly night'' (Moore melody)" , "Frequently, as the poet would have it" , "(Poetically) frequently" , "Many times, of old" , "time and again in literature" .)