Powerful ruler (9)
I believe the answer is:
potentate
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">powerful ruler</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 potentate that I've seen before include "A monarch or ruler" , "authority" , "Powerful autocratic ruler" , "Mogul" .)