Eastern variety of marled stone (7)
I believe the answer is:
emerald
'stone' is the definition.
(thesaurus)
'eastern variety of marled' is the wordplay.
'eastern' becomes 'e'.
'variety of' is an anagram indicator.
'marled' with letters rearranged gives 'merald'.
'e'+'merald'='EMERALD'
(Other definitions for emerald that I've seen before include "Precious gemstone" , "city in Oz?" , "On of the Greens" , "a type employed by the press" , "Green variety of beryl" .)