On-off device (6)
I believe the answer is:
switch
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">on-off device</span>' is the definition.<br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for switch that I've seen before include "Change abruptly" , "Control for making or breaking connections" , "Change; false hair" , "that turns on the power" , "Change; flexible shoot" .)