Mother of Horus (4)
I believe the answer is:
isis
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">mother of horus</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 isis that I've seen before include "Oxford's second eight" , "The upper Thames" , "Revered figure" , "Old Egyptian fertility goddess" , "Oxford's second crew" .)