Brown photo tone (5)
I believe the answer is:
sepia
'brown photo tone' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sepia that I've seen before include "Old drawing" , "Pigment got from cuttlefish ink" , "brownish colour" , "Dark reddish-brown pigment" , "Rich reddish-brown colour" .)