Numbing substance (11)
I believe the answer is:
anaesthetic
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">numbing substance</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 anaesthetic that I've seen before include "Number of bodies - can hesitate (anag)" , "A number of theatres" , "Theatre number" , "Numbing substance" , "painkiller" .)