Western isles? Maybe, but they're in the S. Pacific! (5)
I believe the answer is:
samoa
'western' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for samoa that I've seen before include "Pacific island nation, capital Apia" , "South Pacific island nation" , "Southwest Pacific island group" , "Group of islands in the South Pacific" , "South Pacific island country, gaining its independence from New Zealand in 1962" .)