Occasionally falling from Estonia's volcano (4)
I believe the answer is:
etna
'volcano' is the definition.
(Mount Etna)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for etna that I've seen before include "Constant smoker" , "hotly-tipped runner" , "Heating vessel" , "Highest active volcano in Europe" , "Italian volcano" .)