The aching part, after a punch on the jaw? (4)

I believe the answer is:

chin

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

'the jaw?' is the definition.
(I've seen this in other clues)

'the aching part after a punch' is the wordplay.
'CHIN' is hidden in amongst the letters.
However, I am unsure how the hidden word is indicated.

'on' acts as a link.

Can you help me to learn more?

(Other definitions for chin that I've seen before include "Feature of face" , "Point of the jaw" , "narrow opening" , "Bottom part of jaw" , "Punch to the face" .)

I've seen this clue in the Evening Standard.

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