Short fast race (6)
I believe the answer is:
sprint
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">short fast race</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for sprint that I've seen before include "Quick dash" , "Short fast run" , "Run quickly" , "Short race at full speed" , "quick run" .)