Sea mist represented by a painter (7)
I believe the answer is:
matisse
'a painter' is the definition.
(Henri Matisse, 1869-1954, French artist)
'sea mist represented' is the wordplay.
'represented' indicates an anagram.
'sea'+'mist'='seamist'
'seamist' with letters rearranged gives 'MATISSE'.
'by' acts as a link.
(Other definitions for matisse that I've seen before include "Leading fauvist painter, d. 1954" , "Henri ---, Twentieth Century painter" , "French impressionist" , "Mae sits badly for the French painter" , "20th century French painter" .)