Harry Enfield's wish? (3)

I believe the answer is:

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'wish?' is the definition.
(I've seen this in another clue)

I cannot understand how the rest of the clue works.

(Other definitions for yen that I've seen before include "Longing for a currency unit" , "Have a longing for Japanese money?" , "Long for a coin" , "Unit of money in Japan" , "Longing (colloq.)" .)

I've seen this clue in the Evening Standard.

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