False membership fees reversed in Post Office (6)

I believe the answer is:

pseudo

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

I can't explain the rest of the clue.

(Other definitions for pseudo that I've seen before include "O dupes! being false and insincere" , "Insincere person" , "artificial" , "'Fake, sham (6)'" , "Sham (coll)" .)

I've seen this clue in The Sunday Times and The Times.

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