Cornish town surrenders unknown amount in atonement (7)
I believe the answer is:
penance
'atonement' is the definition.
(I've seen this before)
'cornish town surrenders unknown amount' is the wordplay.
I cannot really see how this works, but
'amount' could be 'en' (en is a kind of amount) and 'en' is found within the answer.
This explanation may well be incorrect...
'in' is the link.
Can you help me to learn more?
(Other definitions for penance that I've seen before include "sackcloth and ashes?" , "Act of contrition" , "Self-imposed punishment" , "humiliating act" , "Voluntary self-punishment" .)