Crossword Genius

Something used in a supporting role? (4)

Ross

I believe the answer is:

prop

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

'something used' is the definition.
I can't judge whether this definition defines the answer.

'a supporting role?' is the wordplay.
'a supporting' becomes 'pro' (I've seen this in other clues).
'role?' becomes 'p' (I can't explain this - if you can you should give a lot more credence to this answer).
'pro'+'p'='PROP'

'in' acts as a link.

Can you help me to learn more?

(Other definitions for prop that I've seen before include "Driving mechanism" , "Lean" , "Moveable object used on stage" , "Stay" , "Support; object used on stage" .)

I've seen this clue in the Evening Standard.
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