Duchess ultimately visits on and off — it's enough for duke (7)
I believe the answer is:
fistful
'duchess ultimately visits on and off' is the definition.
I can't judge whether this definition defines the answer.
'enough for duke' is the wordplay.
'enough' becomes 'ful' (I can't explain this - if you can you should believe this answer much more).
'for' means one lot of letters go next to another (I've seen this in other clues).
'duke' becomes 'fist' (put up your dukes).
'ful' put after 'fist' is 'FISTFUL'.
'it's' is the link.
Can you help me to learn more?
(Other definitions for fistful that I've seen before include "Amount a hand holds" , "amount of dollars?" , "As much as can be held in the hand" , "it should be within one's grasp" , "A -- of Dollars (film)" .)