Best smack will have the highest price (3,5)

I believe the answer is:

top whack

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'the highest price' is the definition.
(I've seen this before)

'best smack will' is the wordplay.
'best' becomes 'top' (top can mean the very best).
'smack will' becomes 'whack' (I can't justify this - if you can you should give a lot more credence to this answer).
'top'+'whack'='TOP WHACK'

'have' is the link.

Can you help me to learn more?

(Another definition for top whack that I've seen is " Highest price".)

I've seen this clue in The Independent.

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