Affect (6)
I believe the answer is:
colour
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">affect</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that colour is a type of act upon)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for colour that I've seen before include "Red or green, say" , "black?" , "Hue, tint" , "Distort; blush; hue" , "Such a sergeant" .)