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 quite see how this works, but
'a' could be 'an' and 'an' is located in the answer.
This explanation may well be incorrect...
'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" .)