Brother of Isaac (4)
I believe the answer is:
esau
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">brother of isaac</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 esau that I've seen before include "Old Testament twin" , "Birthright seller (Bible)" , "Jacob's twin brother" , "Elder of the twin sons of Isaac and Rebecca" , "Old Testament character sounds as if he had a vision" .)