Weapon that makes Jack a junior NCO (5)
I believe the answer is:
lance
'weapon' is the definition.
(lance is a kind of weapon)
'jack a junior nco' is the wordplay.
I cannot really see how this works, but
'a' could be 'an' and 'an' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
'that makes' acts as a link.
Can you help me to learn more?
(Other definitions for lance that I've seen before include "Incise" , "Old cavalry weapon" , "Weapon of knights of old" , "Boy - prick (a boil)" , "Long weapon; prick" .)