Dealer disposed to accept million for stone (7)
I believe the answer is:
emerald
'for stone' is the definition.
(type of gemstone)
'dealer disposed to accept million' is the wordplay.
'disposed' indicates an anagram.
'to accept' indicates putting letters inside.
'million' becomes 'm' (abbreviation).
'dealer' with letters rearranged gives 'eerald'.
'eerald' enclosing 'm' is 'EMERALD'.
(Other definitions for emerald that I've seen before include "and 1 Across: Ireland" , "city in Oz?" , "Precious green stone" , "Led mare (anag.)" , "Gem; type of moth" .)