Burst of speed (6)
I believe the answer is:
sprint
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">burst of speed</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for sprint that I've seen before include "Short fast race" , "Run quickly" , "To make fast progress" , "Short race at full speed" , "quick run" .)