Islander, famous at last, with a grouse (6)
I believe the answer is:
samoan
'islander' is the definition.
(I've seen this before)
'famous at last with a grouse' is the wordplay.
'at last' indicates one should take the final letters.
'with' is a charade indicator (letters next to each other).
'grouse' becomes 'moan' (I've seen this in another clue).
The last letter of 'famous' is 's'.
's'+'a'+'moan'='SAMOAN'
(Other definitions for samoan that I've seen before include "from part of Polynesia" , "Islander" .)