One included in his progeny? (5)

I believe the answer is:

sprog

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'one included' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.

'in his progeny?' is the wordplay.
'in' indicates a hidden word.
'SPROG' is hidden in the letters of 'his progeny'.

Can you help me to learn more?

(Other definitions for sprog that I've seen before include "Child; recruit (mil. slang)" , "Kid" , "Child, colloquially" , "little one" , "Baby (slang)" .)

I've seen this clue in The Times.

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