Active Sicilian volcano (4)
I believe the answer is:
etna
'active sicilian 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 "Sicilian landmark" , "Neat volcano overturned" , "Neat class of volcano in Sicily" , "Impressive mount" , "A neat sort of volcano" .)