Chief, primary (4)
I believe the answer is:
main
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">chief</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I know that chief can be written as main)</span><br/ ><br/ >'<span class="explanation-format__original">primary</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that primary can be written as main)</span><br/ ><br/ ></span>
(Other definitions for main that I've seen before include "river in Germany" , "Most important or greatest in size" , "Most important element" , "Foremost" , "Cardinal" .)