Old-time anesthetic (5)
I believe the answer is:
ether
'old-time anesthetic' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ether that I've seen before include "number" , "Colourless liquid used as a solvent" , "Medium supposedly" , "Chemical solvent" , "There goes the anaesthetic" .)