Mount hotly tipped doesn't always run (4)
I believe the answer is:
etna
'mount' is the definition.
(Etna is an example)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for etna that I've seen before include "Italian smoker" , "source of fumes?" , "Sicilian hothead?" , "Long-term smoker" , "Heating vessel" .)