It's wrong to possess the best, yet make no further advance (4,2)

I believe the answer is:

stop it

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'best yet make no further advance' is the definition.
I don't know anything about this answer so I can't judge whether this works.

'it's wrong to possess the' is the wordplay.
'it's wrong' becomes 'spi' (I can't explain this - if you can you should give a lot more credence to this answer).
'possess' is an insertion indicator.
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'spi' enclosing 'to' is 'stopi'.
'stopi'+'t'='STOP IT'

Can you help me to learn more?

(Other definitions for stop it that I've seen before include "Desist!" , "Don't" .)

I've seen this clue in the Evening Standard.

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