Men involved in the noble art? (5)
I believe the answer is:
dukes
'men involved' is the definition.
I can't judge whether this defines the answer.
'the noble art?' is the wordplay.
'the noble' becomes 'duke' (duke is a kind of noble).
'art?' becomes 's' (I am not sure about this - if you are sure you should believe this answer much more).
'duke'+'s'='DUKES'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for dukes that I've seen before include "Peers of the realm" , "Noblemen" , "Titled gents or slangy fists" , "eg 21, 22 and Plaza-Toro" .)