Realm or dominion (6)
I believe the answer is:
empire
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">realm</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >'<span class="explanation-format__original">dominion</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for empire that I've seen before include "Wide dominion" , "Group of countries ruled by single supreme authority" , "Group of states ruled by one monarch" , "Widespread political or industrial organisation" , "Sovereign state" .)