Thrusting weapon (5)
(Other definitions for spear that I've seen before include "Sharp weapon" , "Weapon to throw" , "Sharp-tipped weapon" , "Long pointed weapon" , "Asparagus shoot" .)
'thrusting weapon' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for lance that I've seen before include "fish" , "Cut open" , "Pierce (a boil)" , "Pointed instrument" , "Weapon of knights of old" .)