Middle ear bone (5)
I believe the answer is:
incus
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">middle ear bone</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for incus that I've seen before include "Bone in the middle ear" , "anvil (so we hear)" , "Hard part of the Listener" , "Ear anvil bone" , "part of sound system" .)