Refers to punishment that finishes men in the ring (5)
I believe the answer is:
penal
'refers to punishment' is the definition.
I can't tell whether this definition defines the answer.
'finishes men in the ring' is the wordplay.
'finishes men' becomes 'n' (I can't explain this - if you can you should give a lot more credence to this answer).
'in the' is an insertion indicator.
'ring' becomes 'peal' (synonyms).
'n' inserted into 'peal' is 'PENAL'.
'that' acts as a link.
Can you help me to learn more?
(Other definitions for penal that I've seen before include "Punishable by law" , "Punishing" , "Punitive" , "Relating to legal punishment" , "Very severe" .)