Crossword Genius

Arm stable adolescent? (4)

Ross

I believe the answer is:

colt

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

'arm stable adolescent?' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.

This is the entire clue.

Can you help me to learn more?

(Other definitions for colt that I've seen before include "Young Arab maybe" , "runner" , "Youngster" , "Rod" , "Male horse under four years of age" .)

I've seen this clue in The Independent.
Want a hint initially instead of a full solution? Install my app