Sister of Osiris
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sister of osiris</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for isis that I've seen before include "Egyptian deity" , "water" , "Wife of Osiris" , "Egyptian goddess and jihadist group" , "Oxford river; goddess" .)