Paste diamond sent on hire, maybe (10)
I believe the answer is:
rhinestone
'paste diamond' is the definition.
The answer and definition can be both substances as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'sent on hire maybe' is the wordplay.
'maybe' indicates anagramming the letters.
'sent'+'on'+'hire'='sentonhire'
'sentonhire' anagrammed gives 'RHINESTONE'.
Can you help me to learn more?
(Other definitions for rhinestone that I've seen before include "imitation gem" , "Fake gem" , "cheap jewellery" , "it's made of paste" , "Rock" .)