Pointers annoy grannies ultimately (7)

I believe the answer is:

needles

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'pointers' is the definition.
(needle is a kind of pointer)

I cannot understand how the rest of the clue works.

(Other definitions for needles that I've seen before include "Heckles" , "Annoys, pointers" , "Western point of the Isle of Wight" , "Slender points of a conifer" , "required by dressmakers?" .)

I've seen this clue in The Sunday Times and The Times.

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