Artist friend going round island by ship (7)
I believe the answer is:
matisse
'artist' is the definition.
(Henri Matisse, 1869-1954, French artist)
'friend going round island by ship' is the wordplay.
'friend' becomes 'mate' (mate is a kind of friend).
'going round' indicates putting letters inside (some letters go around others).
'island' becomes 'i' (geographical abbreviation).
'by' means one lot of letters go next to another.
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'i'+'ss'='iss'
'mate' placed around 'iss' is 'MATISSE'.
(Other definitions for matisse that I've seen before include "Henri --, French artist" , "Henri -, nineteenth-twentieth century French painter/sculptor" , "French painter, d. 1954" , "French painter, Henri, d.1954" , "20th century French painter" .)