Pacific Ocean monarchy (5)
I believe the answer is:
tonga
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">pacific ocean monarchy</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for tonga that I've seen before include "Pacific island state" , "Two-wheeled Indian vehicle" , "Pacific Ocean monarchy" , "South Pacific kingdom, capital Nuku'alofa" , "part of Polynesia" .)