Colour of old photographs (5)
I believe the answer is:
sepia
'colour of old photographs' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for sepia that I've seen before include "Pigment got from cuttlefish ink" , "brownish colour" , "Reddish-brown colour - easy as pie" , "Brownish tint or pigment" , "Brown with a red tinge" .)