Sea-mist reveals French painter (7)
I believe the answer is:
matisse
'french painter' is the definition.
(I've seen this in another clue)
'sea-mist reveals' is the wordplay.
'reveals' is an anagram indicator (I've seen 'revealing' mean this).
'sea'+'mist'='seamist'
'seamist' anagrammed gives 'MATISSE'.
(Other definitions for matisse that I've seen before include "French painter, d. 1954" , "Henri -, Fr. artist" , "French impressionist" , "Leading fauvist painter, d. 1954" , "Henri ---, Twentieth Century painter" .)