Burnt sienna (5)
I believe the answer is:
sepia
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">burnt sienna</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that burnt sienna can be written as sepia)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for sepia that I've seen before include "Rich reddish-brown colour" , "A greyish brown" , "Brown colour of old photo" , "Sort of ink" , "Colour of old photographs" .)