Crossword Genius

Make amends when in agreement (2,3)

Ross

I believe the answer is:

at one

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

'in agreement' is the definition.
(I've seen this before)

'make amends when' is the wordplay.
I cannot quite see how this works, but
'when' could be 'on' (I've seen this in other clues) and 'on' is present in the answer.
The remaining letters 'ate' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for at one that I've seen before include "Agreed" , "time to enjoy 21 and 15 [TURKEY and CRACKERS] s?" , "in harmony" , "In agreement" .)

I've seen this clue in The Globe and Mail.
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