I posted on this elsewhere recently. Probably time I wrote this up as a starter for a sticky note. Cut-and-paste:
There is a known issue with sheet metal pedals where the little folded-and-spot-welded metal box fails, allowing the flap at the rear of the box to pop open under pressure from the master cylinder pushrod as you depress the clutch. The pushrod propels the little white plastic clip back through the now-open box, breaking it on its way out, and in bad cases also bending the pushrod. The pedal now can't operate the clutch master cylinder, so you are left without clutch control.
The clip is there to center the pushrod in the metal box on the pedal, but the incipient failure is of the spot welds on the little box. If you can see any movement of the flaps that make up the box, get it fixed before it fails.
A Seat dealer will replace the pedal, taking out the front seat to get enough room to work. If you have the facilities, the pedal can be repaired by redoing the welds, and making them good ones not little spots.
To sum up: The failure is of the sheet metal pedal construction itself. The plastic clip breaks as a side-effect but replacing the clip won't
help on its own, the pedal must be made good or replaced.
The impact of the clutch master cylinder piston hitting the back of the cylinder can cause the seals to fail, leading to hydraulic fluid leaking into the footwell, and a slow, repeated failure of the clutch due to lack of fluid - you fill it up thinking you've solved the
problem only for it to leak away again. This can only be solved by a new master cylinder, I believe, as the seal kits aren't availabile?