Large slide of snow or stone (9)
I believe the answer is:
avalanche
'large slide of snow or stone' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for avalanche that I've seen before include "frightening fall" , "Large mass of sliding snow or stone" , "serious fall" , "Rapid movement of a large mass of snow or ice" , "Disastrous snowfall" .)