I must be ousted from Italian city in revolution (4)
I believe the answer is:
turn
'revolution' is the definition.
(I've seen this before)
'i must be ousted from italian city' is the wordplay.
'must be ousted from' indicates named letters should be taken away.
'italian city' becomes 'turin' (I've seen this before).
'turin' with 'i' taken away is 'TURN'.
'in' acts as a link.
(Other definitions for turn that I've seen before include "Rotate - diverge - change" , "Swing round" , "Revolve; act" , "Go; spin (cricket)" , "Shape (using a lathe)" .)