Betting notes on implement (5)

I believe the answer is:

spade

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

'implement' is the definition.
(I know that spade is a type of garden tool)

'betting notes' is the wordplay.
'betting' becomes 'spa' (I can't justify this - if you can you should give a lot more credence to this answer).
'notes' becomes 'de' (two musical notes).
'spa'+'de'='SPADE'

'on' acts as a link.

Can you help me to learn more?

(Other definitions for spade that I've seen before include "10

I've seen this clue in The Mirror.

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