Rule as monarch (5)
I believe the answer is:
reign
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">rule as monarch</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for reign that I've seen before include "Hegemony" , "Niger (anag)" , "Period of monarch" , "Rule of monarch" , "Wield the sceptre" .)