Gravity-powered vehicle (4)
I believe the answer is:
sled
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">gravity-powered vehicle</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 sled that I've seen before include "Sleigh" , "Vehicle on runners" , "Winter transport" , "Tray on which to slide" , "Goods vehicle" .)