Make a mistake losing top address in Munich (3)

I believe the answer is:

err

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'make a mistake' is the definition.
(I've seen this before)

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

(Other definitions for err that I've seen before include "Drop a clanger" , "Blunder" , "Boob" , "Slip up" , "Make a wrong move" .)

I've seen this clue in the Irish Times (Crosaire) and the Irish Times.

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