It’s the sign of a celebrity (9)

I believe the answer is:

autograph

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'it's the sign' is the definition.
(I've seen this before)

I cannot understand how the remainder of the clue works.

(Other definitions for autograph that I've seen before include "a collector's item perhaps" , "A signature given as souvenir" , "Signer will give this" , "Sign" , "Famous person's signature" .)

I've seen this clue in The Hindu.

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