Rival of Nike (6)
I believe the answer is:
adidas
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">rival of nike</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for adidas that I've seen before include "Sportswear company" , "kit supplier" .)