Stone cut with diamonds is uneven (6)
I believe the answer is:
jagged
'uneven' is the definition.
('jagged' can be similar in meaning to 'uneven')
'stone cut with diamonds' is the wordplay.
I cannot really understand how this works, but
'cut' could be 'jag' (jagging is a kind of cutting) and 'jag' is located in the answer.
'diamonds' could be 'd' (abbreviation in bridge say) and 'd' is found within the answer.
The remaining letters 'ge' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'is' is the link.
Can you help me to learn more?
(Other definitions for jagged that I've seen before include "Having a sharply uneven surface or outline" , "Serrated" , "With rough sharp points" , "Having sharp uneven surface" , "Notched; rough-edged; uneven" .)