Blindingly bright (4)
I believe the answer is:
neon
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">blindingly bright</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for neon that I've seen before include "Atomic number 10" , "Gas - light" , "Could it brighten proceedings" , "Gas used in fluorescent lamps" , "Type of lighting" .)