Car; move quickly (5)
I believe the answer is:
motor
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">car</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(motor can informally mean a car)</span><br/ ><br/ >'<span class="explanation-format__original">move quickly</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for motor that I've seen before include "Car; travel quickly" , "Internal combustion engine" , "Move fast" , "Car - car's engine" , "(Transport using) engine" .)