Flashing light (6)
I believe the answer is:
strobe
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">flashing light</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 strobe that I've seen before include "Light that seems to spin" , "High-intensity flashing beam of light" , "Flasher" , "something flashy" , "Flashing-light device" .)