Provide sound lacking, at its core, tonal balance (9)

I believe the answer is:

equipoise

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'balance' is the definition.
(synonyms)

'provide sound lacking at' is the wordplay.
'provide' becomes 'equip' (equipping is a kind of providing).
'sound lacking at' becomes 'oise' (I can't explain this - if you can you should give a lot more credence to this answer).
'equip'+'oise'='EQUIPOISE'

'its core tonal' acts as a link.
This may not be right. Some or all of it may belong to another bit of the clue.

Can you help me to learn more?

(Another definition for equipoise that I've seen is " balance".)

I've seen this clue in The Hindu.

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