William and Harry say they’re up for a fight? (5)
I believe the answer is:
dukes
I'm afraid I can't even guess how this answer relates to the clue.
Can you help me to learn more?
(Other definitions for dukes that I've seen before include "Noblemen" , "Titled gents or slangy fists" , "Peers of the realm" , "eg 21, 22 and Plaza-Toro" .)