Make restitution at lunchtime (5)

I believe the answer is:

atone

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'make restitution' is the definition.

'at lunchtime' is the wordplay.
'lunchtime' becomes 'one' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'at'+'one'='ATONE'

Can you help me to learn more?

(Other definitions for atone that I've seen before include "Make up for wrong done" , "Make redress" , "In agreement - sounds singular" , "Expiate" , "Make amends, being at one" .)

I've seen this clue in the Evening Standard.

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