Arsenal provides example of this weapon (4)
I believe the answer is:
club
'this weapon' is the definition.
(weapon for hitting people with)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for club that I've seen before include "Stout stick, card suit and association" , "Place to meet one's friends with a weapon" , "Bat - society" , "Kind of weapon or golf stick" , "Association of people with similar interests" .)