Overwhelming victory — natural disaster (9)
I believe the answer is:
landslide
I believe this is a double definition.
'overwhelming victory' is the first definition.
(I've seen this in another clue)
'natural disaster' is the second definition.
(I know that landslide is a type of slide)
(Other definitions for landslide that I've seen before include "Huge majority at election" , "Shifting of ground" , "Runaway" , "Massive election win" , "easy victory" .)