Time to switch off! (6,3)
I believe the answer is:
lights out
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">time to switch off</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 lights out that I've seen before include "Go to sleep!" , "Bedtime signal" , "when one should be ready to retire" , "when it gets dark" , "Suddenly disappears" .)