Something impressed in unled rebellion (7)

I believe the answer is:

edition

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'something impressed' is the definition.
(I've seen this before)

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

Can you help me to learn more?

(Other definitions for edition that I've seen before include "Volume" , "Issue of a publication" , "I die not (anag)" , "Particular form of a book" , "Version of a publication" .)

I've seen this clue in The Sun.

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