Precious stone reportedly contains energy (5)
I believe the answer is:
joule
'energy' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'precious stone reportedly' is the wordplay.
'precious stone' becomes 'jewel' (jewel is a kind of precious stone).
'reportedly' indicates a 'sounds like' (homophone) clue.
'jewel' is a homophone of 'JOULE'.
'contains' is the link.
Can you help me to learn more?
(Other definitions for joule that I've seen before include "SI unit of energy" , "physicist" , "SI unit of work/energy" .)