Prince Harry's dukedom (6)
I believe the answer is:
sussex
'prince harry's dukedom' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sussex that I've seen before include "Coastal county" , "County cricket club" , "Historic English county" , "Historic S. coast county" , "East and West English county" .)