With "Before two, ideally," is in really good form (2,4,4)

I believe the answer is:

at ones best

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

'with before two ideally is in really' is the definition.
I can't tell whether this definition defines the answer.

'good form' is the wordplay.
I cannot quite understand how this works, but
'good' could be 'best' (associated in meaning) and 'best' is located in the answer.
The remaining letters 'atones' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...

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