Europe's highest active volcano (4)
I believe the answer is:
etna
'europe's highest active volcano' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for etna that I've seen before include "Italian volcano" , "Constant smoker" , "burning mountain" , "A neat sort of volcano" , "Highest peak in Italy south of the Alps" .)