Cash contribution to a happy ending (3)

I believe the answer is:

yen

I'm a little stuck... Click here to teach me more about this clue!

'cash' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.

'contribution to a happy ending' is the wordplay.
'contribution to' says the answer is hidden in the clue.
'YEN' can be found hidden inside 'happy ending'.

Can you help me to learn more?

(Other definitions for yen that I've seen before include "money in Tokyo" , "foreign currency" , "Currency of Japan" , "Longing, hankering after" , "Longing (colloq.)" .)

I've seen this clue in the Evening Standard.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.

Connecting...