Scientists make revolutionary vapours (8)
I believe the answer is:
chemists
'scientists' is the definition.
(chemist is a kind of scientist)
'revolutionary vapours' is the wordplay.
'revolutionary' becomes 'che' (Che Guevara the Marxist revolutionary).
'vapours' becomes 'mists' (I am not sure about this - if you are sure you should believe this answer much more).
'che'+'mists'='CHEMISTS'
'make' is the link.
Can you help me to learn more?
(Other definitions for chemists that I've seen before include "They're trained in the natural sciences" , "Pharmacists, say" , "They fill prescriptions by doctors" , "Scientists" , "pair of Boots?" .)