Line of hereditary rulers (7)
I believe the answer is:
dynasty
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">line of hereditary rulers</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 dynasty that I've seen before include "Empire" , "Series of hereditary rulers" , "Succession of relatives" , "rule" , "TV series" .)