Delicate material pierced by new weapon (5)
I believe the answer is:
lance
'weapon' is the definition.
(lance is a kind of weapon)
'delicate material pierced by new' is the wordplay.
'delicate material' becomes 'lace' (I've seen this before).
'pierced by' means one lot of letters goes inside another (some letters pierce a hole in others).
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'lace' enclosing 'n' is 'LANCE'.
(Other definitions for lance that I've seen before include "Pierce (a boil)" , "Horseman's long weapon" , "Shafted weapon used on horseback" , "Incise" , "Weapon of knights of old" .)