Stopping device (5)
I believe the answer is:
brake
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">stopping device</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 brake that I've seen before include "Slower" , "Device for slowing or stopping car" , "Constraint" , "Thicket; estate car" , "Restraint on vehicle" .)