Weapon for pointing, perhaps (5)

I believe the answer is:

arrow

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'weapon' is the definition.
(I know that Arrow is a type of ASM)

I don't understand how the rest of the clue works.

(Other definitions for arrow that I've seen before include "Missile with a straight thin shaft" , "Keepsake" , "What's shot from a bow" , "Projectile from bow" , "Missile fired from bow" .)

I've seen this clue in the Evening Standard.

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