Old photo tone (5)
I believe the answer is:
sepia
'old photo tone' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for sepia that I've seen before include "Reddish-brown colour - easy as pie" , "Former photographic pigment" , "Brown pigment produced from cuttlefish ink" , "Dark reddish-brown pigment" , "Reddish brown -- ie sap (anag)" .)