Clutch Judder is where your transmission starts to vibrate and vibrate even the shifter in your car.
Clutch Judder is most commonly caused by oil or hydraulic oil that makes it way to and accumulates on the clutch itself.
When oil collects on the clutch this causes the clutch to not grip like it should which then causes the clutch judder.
A worn bearing, worn clutch or even a warped or bad flywheel can cause clutch judder as well.