Drug producing numbness or stupor (8)
I believe the answer is:
narcotic
'drug producing numbness or stupor' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for narcotic that I've seen before include "Stupor-inducing drug" , "Drug producing numbness and stupor" , "Addictive drug affecting mood or behaviour" , "Drug to induce drowsiness or stupor" , "Drug that produces numbness or stupor" .)