Straight guy, one found in a cage (4,3)

I believe the answer is:

true rib

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

'one found in a cage' is the definition.
I can't judge whether this defines the answer.

'straight guy' is the wordplay.
'straight' becomes 'true' (synonyms).
'guy' becomes 'rib' (both can mean to tease).
'true'+'rib'='TRUE RIB'

Can you help me to learn more?

(Other definitions for true rib that I've seen before include "One attached directly to sternum" , "fixed bone" , "Bone attached to the breastbone" , "under the skin" , "part of body" .)

I've seen this clue in The Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.