Take back a pledge made to uncle (6)

I believe the answer is:

redeem

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'take back' is the definition.
(I've seen this in another clue)

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

(Other definitions for redeem that I've seen before include "Make good" , "Get back" , "Cash in shares, bonds etc" , "Recover from the pawnshop" , "Buy black, or convert into cash" .)

I've seen this clue in the Evening Standard.

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