Contests of speed (5)
I believe the answer is:
races
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">contests of speed</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for races that I've seen before include "Competitive trials of speed" , "Operates at excessive speed" , "Running competitions" , "Speed contests for horses, cars etc" , "Scare in sporting contests" .)