Creak is caused by clutch master cylinder operating rod moving (sliding outwards towards retaining clip) on the clutch pedal operating projection. Get down on your hands and knees on the ground outside the car and have a look and all will be obvious.
If you leave this condition without doing anything about it, eventually the retaining clip will fracture and the master cylinder rod will come off the clutch pedal projection and you will have no clutch!!!!
You can fix this problem by removing the retaining clip (put a piece of cloth in the top of the foot rest, otherwise the clip will disappear down the inside of the footrest) and packing the slack movement with spacer washers. This will eliminate the movement and pressure of the clutch master cylinder operating rod on the retaining clip and it will not fracture through fatigue.
Make sure you lubricate the clutch pedal projection with a little light oil, WD40, or similar.
Your creaks will now have disappeared and if they come back again one day in the future, just a few drops of light oil again will fix the problem.