Rebel king I turn to (4)
I believe the answer is:
riot
'rebel' is the definition.
(both can mean to cause a disturbance)
'king i turn to' is the wordplay.
'king' becomes 'R' (abbreviation for rex, king in Latin).
'turn' is a reversal indicator.
'to' in reverse letter order is 'ot'.
'r'+'i'+'ot'='RIOT'
(Other definitions for riot that I've seen before include "Disturbance of the peace by many" , "Civil disturbance" , "Violent disturnance of the peace (by crowd)" , "Disturbance by unruly mob" , "Wild revelry" .)