Pound tip of blade into unyielding weapon (7)
I believe the answer is:
halberd
'weapon' is the definition.
(I know that halberd is a type of pike)
'pound tip of blade into unyielding' is the wordplay.
'pound' becomes 'L' (the pound sign is based on an L).
'tip of' suggests removing the centre (I've seen 'tips of' mean this).
'into' indicates putting letters inside.
'unyielding' becomes 'hard' (I've seen this in another clue).
'blade' with its centre removed is 'be'.
'l'+'be'='lbe'
'lbe' inserted within 'hard' is 'HALBERD'.
(Other definitions for halberd that I've seen before include "Old weapon" , "Sharp instrument" , "Combined spear and battleaxe" , "Ancient weapon" , "Ancient battle-axe" .)