Magna Carta king (4)
I believe the answer is:
john
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">magna carta king</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 john that I've seen before include "With nineteen accross twentieth century US actor known for westerns, etc" , "Trick" , "Old King" , "Wayne, Denver or Elton?" , "Magna Carta king" .)