Does your tractor sit alot between use? Is it exposed to weather?
I one the same machine. I would spray some PB blaster on the pivot points and rods that are outside of the case.
Adjustment would be next.
If I recall correctly there is an access door to the clutch on the clutch pedal side of the tractor. You can remove it and see the clutch assembly.
I suspset that your throwout bearing is possibly sticking. Not siding as it should. Look for a grease fitting on the bearing. I read long ago that some of them had one and some did not. But that would only grease the bearing itself. Not the contact area of the inner race to the transmission shaft.
Either way you should be able to shin a light in there and see whatbis causing it to hang up.