O'er and o'er (3)
I believe the answer is:
oft
'o'er and o'er' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for oft that I've seen before include "Frequently, as the poet would have it" , "time and again in literature" , "Frequently in archaic term" , "Old song'... in the stilly night'" , "Frequently, in verse" .)