Legal document unaffected by revolution (4)

I believe the answer is:

deed

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'legal document' is the definition.
(I know that deed is a type of legal document)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for deed that I've seen before include "What's done" , "Action - legal document" , "A conscious action" , "Conscious act" , "Feat" .)

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