More than likely a seized clutch arm, they have a tendency to seize up where the shaft goes through the housing especially if they have been standing a while. Can be freed up but they are a bit awkward to do, Mine was getting a bit stiff, but I had it sorted when the clutch was replaced a couple of years ago. It was removed, cleaned and re greased.
Try some penetrating oil and see if you can work it loose, you may need someone to operate the clutch while you try to lubricate the arm.
You can access it from the top if you remove the engine access panel. Don't use WD40 as its not a true penetrating oil. Plus gas or Rocal or similar make is best.
Sundance