Reassembled spare weapon (5)
I believe the answer is:
spear
'weapon' is the definition.
(I know that spear is a type of weapon)
'reassembled spare' is the wordplay.
'reassembled' is an anagram indicator.
'spare' is an anagram of 'SPEAR'.
(Other definitions for spear that I've seen before include "Shafted weapon for throwing or thrusting" , "Thrown weapon" , "stick" , "Asparagus shoot" , "Long pointed weapon" .)