clutch pedal free play decreases
You cannot physically put a clutch disk in backwards unless you force it together. If you do this you will destroy the clutch disc and possibly other clutch components.
First you may have gotten oil or grease on the disc or clutch friction plates. Next check your adjustments, the current pedal adjustments may not allow the clutch to sit properly on the disc, as a clutch wears ofetn people will adjust the pedal travel to allow a few more months use out of it, you will nee to back it off.
The pressure plate which forces the friction disc against the flywheel by means of spring plates. Pressing the clutch pedal down forces the pressure plate away from the friction disc and power transfer from engine to transmission is broken.
hydraulic single disc clutch
If the disc is installed correctly the clutch will engage and disengage smoothly. In most cases if the disc is installed backwards the clutch disc will bind against the flywheel/crankshaft bolts and not release resulting with a clutch that doesn't disengage. More than likely if the disc was installed backwards the disc is now damaged and will need to be replaced.
You replace it. The oil is in the clutch face and if you use it, the face will come off of the disc. There is no way to clean it.
Clutch disc is worn out. Not knowing what vehicle you have, most are hydraulically operated and there is no adjustment. Time for clutch replacement.
no adjustment on hydraulic clutch, worn clutch disc and pressure plate
Between the two clutch facings
Clutch disc, pressure plate, transmission shaft,
A clutch consists of a shaft coming from the engine with a round plate mounted on it, called the 'flywheel', a disc made of some ablative material, which is connected to the transmission, a pressure plate, which squeezes the clutch disc against the flywheel, and a throw-out bearing, which is how the force to disengage the clutch is applied to the pressure plate. When a clutch goes out, the parts often come loss, and can damage other parts if the engine is kept operating for very long or at high RPMs. The most common cause of clutch failure is the ablative material of the clutch disc wears down to the point where it comes apart when it contacts the flywheel. If the vehicle is driven when this happens, it can result in the pressure plate and flywheel having to be replaced. A clutch which won't disengage, but does not slip indicates a broken throw-out bearing, which means parts thereof are flying around the clutch housing. In any case, this requires major mechanical work to repair properly.
If it has a hydraulic clutch, I believe they can not be adjusted. When the pedal travel is no longer acceptable the clutch disc must be replaced.