Early anesthetic (5)
I believe the answer is:
ether
'early 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 "Liquid used as anaesthetic/ solvent" , "Some were put out by this" , "number" , "I'm volatile" , "Imaginary interstellar medium" .)