Create trouble (4,3,4)
I believe the answer is:
rock the boat
'create trouble' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for rock the boat that I've seen before include "as the sea may?" , "Yachtsman's motion might" , "make trouble" , "Disturb a harmonious situation" , "Disturb the status quo" .)