It's done up again (4)

I believe the answer is:

deed

I'm a little stuck... Click here to teach me more about this clue!

'it's done' is the definition.
(I've seen this in another clue)

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

Can you help me to learn more?

(Other definitions for deed that I've seen before include "Legal document for transfer of property" , "documentary evidence" , "Action - legal document" , "Act - exploit - legal document" , "Conscious act" .)

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