Pacific island; the world's smallest republic (5)
I believe the answer is:
nauru
This clue is a double definition.
'pacific island' is the first definition.
(I've seen this before)
'the world's smallest republic' is the second definition.
(I've seen this in another clue)
(Other definitions for nauru that I've seen before include "Small Pacific republic" , "SW Pacific republic" , "Fairground carousel" , "Pacific coral island republic, once rich in phosphates" , "Island country in Micronesia" .)