Nation west of Tonga (4)
I believe the answer is:
fiji
'nation west of tonga' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for fiji that I've seen before include "South Pacific country, capital Suva" , "Group of islands in the South Pacific" , "South Pacific country of some 840 islands" , "Island country 1,300 miles north-east of New Zealand" , "Island group in the south Pacific" .)