Stop signal (3,5)
I believe the answer is:
red light
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">stop signal</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 red light that I've seen before include "Warning signal" , "Indication of immoral area" , "Don't go through it!" , "Stop signal" , "Signal not to go on!" .)