Weapon's spike catching knight (5)
I believe the answer is:
lance
'weapon's' is the definition.
(lance is a kind of weapon)
'spike catching knight' is the wordplay.
'spike' becomes 'lace' ('lace' can be a synonym of 'spike').
'catching' is an insertion indicator.
'knight' becomes 'n' (chess).
'lace' placed around 'n' is 'LANCE'.
(Other definitions for lance that I've seen before include "One like pike" , "Boy - prick (a boil)" , "Pointed instrument" , "Jousting weapon" , "Long-shafted weapon" .)