Chap twice in prison for arson (3)

I believe the answer is:

son

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'chap' is the definition.

'twice in prison for arson' is the wordplay.
'SON' is hidden in amongst the letters.
But, I'm not sure how the hidden word is indicated.

Can you help me to learn more?

(Other definitions for son that I've seen before include "Young boy" , "Male scion" , "Male child" , "Male descendant" , "Heir" .)

I've seen this clue in the Evening Standard.

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