Hard rubber (7)
I believe the answer is:
ebonite
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">hard rubber</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for ebonite that I've seen before include "Bee on it (anag.)" , "Rubbery material" , "vulcanised rubber" , "something rubbery" , "Vulcanite" .)