Service no longer used by gunners (10)
I believe the answer is:
cannonball
'service no longer used by gunners' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe you can see an association between them that I don't see?
'service no' is the wordplay.
I cannot quite understand how this works, but
'no' could be 'non' (I've seen this in other clues) and 'non' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for cannonball that I've seen before include "Big shot" , "one fired long ago" , "Old projectile" , "Battlefield projectile" .)