Dentine; piano key (5)
I believe the answer is:
ivory
I believe this clue is a double definition.
'dentine' is the first definition.
(ivory is a kind of dentine)
'piano key' is the second definition.
(I've seen this before)
(Other definitions for ivory that I've seen before include "Off-white colour" , "Cream" , "Jumbo's dentine" , "What may be carved" , "What tusks are made of" .)