Be first (4)
I believe the answer is:
lead
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">be first</span>' is the definition.<br/ ><span class="explanation-format__explanation">(lead can mean leading or primary)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for lead that I've seen before include "Chemical element, symbol Pb" , "Guide; precede" , "first name in lights?" , "Show the way; soft metallic element" , ""bullets"" .)