Noble fellows useful in a punch-up (5)

I believe the answer is:

dukes

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'useful in a punch-up' is the definition.
I can't tell whether this definition defines the answer.

'noble fellows' is the wordplay.
'noble' becomes 'duke' (duke is a kind of noble).
'fellows' becomes 's' (I can't justify this - if you can you should believe this answer much more).
'duke'+'s'='DUKES'

Can you help me to learn more?

(Other definitions for dukes that I've seen before include "Peers of the realm" , "Noblemen" , "eg 21, 22 and Plaza-Toro" , "Titled gents or slangy fists" .)

I've seen this clue in the Evening Standard.

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