Convincing victory (9)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
landslide
'convincing victory' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for landslide that I've seen before include "Overwhelming election win" , "convincing victory" , "Shifting of ground" , "Overwhelming victory in election, or a natural disaster" , "easy victory" .)