Pacific island (4)
I believe the answer is:
guam
'pacific island' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for guam that I've seen before include "Largest of the Mariana Islands" , "US island east of the Philippines" , "place in the Marianas" , "NW Pacific island with large US base" , "Island in the West Pacific" .)