Crossword Genius

Riverside memo worth ten dollars, say (4-4)

Ross

I believe the answer is:

bank-note

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

'dollars say' is the definition.
(I know that Dollar bill is a type of bank note)

'riverside memo worth ten' is the wordplay.
I cannot quite see how this works, but
'riverside' could be 'bank' (I've seen this before) and 'bank' is present in the answer.
'memo' could be 'note' (I've seen this in another clue) and 'note' is found within the answer.
No letters remain.
This explanation may well be incorrect...

Can you help me to learn more?

I've seen this clue in the Sydney Morning Herald.
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