Christabel's boy (4)

I believe the answer is:

abel

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'boy' is the definition.

'christabel's' is the wordplay.
'ABEL' is hidden within the letters.
But, I am not sure how the hidden word is indicated.

Can you help me to learn more?

(Other definitions for abel that I've seen before include "Bale out with murder victim" , "Adamson" , "character in the Bible" , "Victim of 11" , "Cain's 11" .)

I've seen this clue in the Evening Standard.

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