Crossword Genius

Face pulled by prisoners having to help out (4)

Ross

I believe the answer is:

pout

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

'face' is the definition.
(I know that pout is a type of face)

'pulled by prisoners having to help out' is the wordplay.
'POUT' is hidden within the letters.
But, I'm unsure how the hidden word is indicated.

Can you help me to learn more?

(Other definitions for pout that I've seen before include "Petulant look; fish" , "Look sulky" , "prepare for selfie?" , "Push lips out as sign of annoyance" , "set of lips" .)

I've seen this clue in The Irish Times.
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