Very dark brown or black (5)
I believe the answer is:
ebony
I believe this is a double definition.
'very dark brown' is the first definition.
(I've seen this before)
'black' is the second definition.
(I know that ebony is a type of black)
(Other definitions for ebony that I've seen before include "hard stuff" , "Hard dark-coloured wood" , "Very dark brown" , "Wood - Boyne (anag)" , "Heavy hard wood, usually black" .)