Gas or brake (5)
I believe the answer is:
pedal
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">gas or brake</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for pedal that I've seen before include "Power a bike" , "cause a revolution in cycling?" , "Travel by bike" , "part of organ" , "Foot-lever" .)