Sister and wife of Zeus (4)
I believe the answer is:
hera
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sister and wife of zeus</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 hera that I've seen before include "Greek queen of Olympian gods" , "Divinity" , "Greek equivalent of Juno" , "female Greek deity" , "marriage goddess" .)