Brownish photo tint (5)
I believe the answer is:
'brownish photo tint' 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 "Reddish-brown colour as in old photos" , "Sort of ink" , "Pigment obtained from cuttlefish ink" , "Reddish-brown; cuttlefish ink" , "Brown pigment produced from cuttlefish ink" .)