She's stony (5)
I believe the answer is:
'she's' is the definition.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for beryl that I've seen before include "Emerald or aquamarine" , "Transparent mineral used as a gemstone" , "- Bainbridge, English novelist" , "Girl's name - gemstone" , "Coloured stone" .)