Hard dark wood (5)
I believe the answer is:
ebony
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">hard dark wood</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(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" .)