Crossword Genius

Punishment one really feels (4)

Ross

I believe the answer is:

pain

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

'punishment' is the definition.
(thesaurus)

'one really feels' is the wordplay.
I cannot quite see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is present in the answer.
The remaining letters 'pan' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for pain that I've seen before include "Sensation of hurt" , "Physical discomfort" , "Agony" , "Suffering, ache" , "Suffering, distress" .)

I've seen this clue in the Evening Standard.
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