Precious stone dealer scrambled to receive first piece of malachite (7)
I believe the answer is:
emerald
'precious stone' is the definition.
(emerald is a kind of precious stone)
'dealer scrambled to receive first piece of malachite' is the wordplay.
'scrambled' indicates anagramming the letters.
'to receive' indicates putting letters inside.
'first piece of' suggests taking the first letters.
The first letter of 'malachite' is 'm'.
'dealer' is an anagram of 'eerald'.
'eerald' enclosing 'm' is 'EMERALD'.
(Other definitions for emerald that I've seen before include "Highly-valued variety of beryl" , "Led mare (anag.)" , "city in Oz?" , "and 1 Across: Ireland" , "Precious green stone" .)