Stir violently; perturb (7)
I believe the answer is:
This clue is a double definition.
'stir violently' is the first definition.
(I've seen this before)
'perturb' is the second definition.
(I've seen this in another clue)
(Other definitions for agitate that I've seen before include "Disturb or shake" , "Trouble, make nervous" , "Stir vigorously" , "Make troubled or nervous" , "Disturb, cause to worry" .)