Overturn or unsettle (5)
I believe the answer is:
upset
I believe this is a double definition.
'overturn' is the first definition.
(I know that overturn can be written as upset)
'unsettle' is the second definition.
(I know that unsettle is a more specific form of the action the upset)
(Other definitions for upset that I've seen before include "Disconcert" , "Disconcerted, discomposed" , "Overturn, disturb" , "Disturb the balance or stability of" , "Unhappy - unexpected defeat" .)