Dull photo finish (5)
I believe the answer is:
matte
'dull photo finish' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for matte that I've seen before include "Mask used in film; ET mat (anag.)" , "Mask used to add an image in front of camera" , "Dull, flat" , "A dull finish" , "Mask used to record two images on same film" .)