Impossible to hear (9)
I believe the answer is:
inaudible
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">impossible to hear</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 inaudible that I've seen before include "Unable to be heard" , "Not aurally detectible" , "Cannot be heard" , "Impossible to hear" , "impossible to grasp" .)