Hard dark wood (5)
I believe the answer is:
ebony
'hard dark wood' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ebony that I've seen before include "Wood - Boyne (anag)" , "Tree with blackish wood" , "Hard dark-coloured wood" , "'Hard, dark wood (5)'" , "Black hardwood" .)