Harry Enfield's wish? (3)
I believe the answer is:
'wish?' is the definition.
(I've seen this in another clue)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(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.)" .)