All vehicles with a manual transmission will have a friction clutch between the engine and gearbox, allowing the driver to pull away from a standstill and change gears. Clutches are hard wearing, but do need periodic replacement as the clutch wears down.
Identify the symptoms of a worn clutch.
Usually this is characterised by the clutch slipping as you apply power- the engine speed will increase greatly when you try to accelerate, even though the clutch pedal is not pressed. Under normal driving, a healthy clutch will 'lock' the engine to the transmission, so its speed should be directly linked to changes in the vehicle speed.
Make sure the clutch itself is at fault.
If your vehicle has a hydraulically-operated clutch, eliminate air in the system by bleeding the hydraulic circuit, as you would with the braking system. A cable-operated clutch could be suffering from a seized or jammed cable, preventing the clutch from taking the full torque from the engine.
Have the clutch replaced as soon as possible.
Clutch replacement is an involving job, requiring removal of the transmission to access the clutch. Unless you are an experienced home mechanic, book your car into a this garage to have the work done.