How much is it worth at the banks in Japanese money? (3,4)
I believe the answer is:
say when
'worth at the banks in japanese money?' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.
'how much is it' is the wordplay.
I cannot really see how this works, but
'it' could be 'sa' (SA can mean sex appeal, as in 'it') and 'sa' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for say when that I've seen before include "Request to be told to stop pouring drink" , "Words from the pourer?" , "Pourer's words" , "Tell me when to stop pouring" .)