Artist left in Eastern sea that's green (7)
I believe the answer is:
emerald
'green' is the definition.
(I've seen this before)
'artist left in eastern sea' is the wordplay.
'artist' becomes 'ra' (Royal Academician, member of Royal Academy of Arts).
'left' becomes 'l' (common abbreviation**).
'in' indicates putting letters inside.
'eastern' becomes 'e'.
'sea' becomes 'med' (abbreviation of Mediterranean).
'ra'+'l'='ral'
'e'+'med'='emed'
'ral' going inside 'emed' is 'EMERALD'.
'that's' is the link.
(Other definitions for emerald that I've seen before include "Small size of type, in printing" , "Ireland is often called The .......Isle" , "Green like this isle" , "and 1 Across: Ireland" , "Green - jewel" .)