Weapons a regimental sergeant major can provide (4)
I believe the answer is:
arms
'weapons' is the definition.
('arm' can be a synonym of 'weapon')
'a regimental sergeant major can provide' is the wordplay.
I cannot really understand how this works, but
'a' is present in the answer.
The remaining letters 'rms' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for arms that I've seen before include "Weapons, collectively" , "Ordnance" , "See 11" , "branches" , "pacifists won't take up" .)