Music producers apply pressure over hits (7-5)

I believe the answer is:

squeeze-boxes

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'music producers apply' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.

'pressure over hits' is the wordplay.
'pressure' becomes 'squeeze' (squeeze is a kind of pressure).
'over hits' becomes 'boxes' (I can't explain this - if you can you should give a lot more credence to this answer).
'squeeze'+'boxes'='SQUEEZE-BOXES'

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I've seen this clue in The Sunday Times.

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