A sharp, pointed item, said to be used during aggressive act (6)
I believe the answer is:
attack
'act' is the definition.
(attack is a kind of act)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for attack that I've seen before include "Assault - assail" , "Fiercely criticise" , "Hit out" , "Ambush - mug - criticise - fit" , "Raid" .)