An actuator with a simple function for the control of a friction clutch in the drive train of a motor vehicle having a cylinder/piston unit for generating the contact pressure of the clutch should be fast, inherently safe and nevertheless simple and inexpensive. For this purpose, a controllable pump (3) generates a pressure medium and makes it available to the cylinder/piston unit (1) via a self-regulating valve unit (2). A dump valve (8) consists of a sleeve (10) and a spring-assisted slide (12) therein. The sleeve has a first opening (11), through which the pressure medium can flow from the cylinder/piston unit (1). The slide (12) exposes the opening (11) in a first position and conceals the opening of a second position. The clutch is controlled in this way by actuating the electric motor.