Sticker finally put on first compartment (7)

I believe the answer is:

bayonet

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'sticker' is the definition.
(weapon for stabbing or sticking people)

I can't explain the remainder of the clue.

(Other definitions for bayonet that I've seen before include "Stabbing weapon" , "Pointed weapon" , "one's attached to one's rifle - that's sort of fitting" , "Dagger attached to 26 Across" , "Kind of knife attached to a rifle" .)

I've seen this clue in The Times.

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