Blackish wood (5)
I believe the answer is:
ebony
'blackish wood' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for ebony that I've seen before include "hard stuff" , "Hard wood used for black piano keys and in cabinetwork" , "Heavy hard wood, usually black" , "Hard dark-coloured wood" , "Tree with blackish wood" .)