Upsets or stirs up (8)
I believe the answer is:
disturbs
I believe this is a double definition.
'upsets' is the first definition.
(I know this)
'stirs up' is the second definition.
('disturb' can be a synonym of 'stir up')
(Other definitions for disturbs that I've seen before include "Upsets or stirs up" , "Upsets or troubles" , "Breaks the quiet or calm of" , "Interferes with peace or order" .)