Nation on the Gulf of Oman (4)
I believe the answer is:
iran
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">nation on the gulf of oman</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for iran that I've seen before include "It used to be Persia" , "oil supplier" , "Modern name for Persia" , "Persia some time ago" , "Middle Eastern country" .)