Reddening cosmetic (5)
I believe the answer is:
rouge
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">reddening cosmetic</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 rouge that I've seen before include "Face paint" , "Red make-up" , "Cheek colouring" , "struggle at Eton" , "Wheel shows this" .)