Lose brightness (4)
I believe the answer is:
fade
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">lose brightness</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 fade that I've seen before include "Bleach or decline" , "Wither away" , "Dwindle" , "Droop" , "Waste away" .)