Strong rubbing when clutch pressed

Hi, I'm hoping someone can help me as I'm lost. I parked my vehicle up, no issues when I left and returned to it two weeks later; to find it starts fine and still selects gears, but when clutch is pressed all the way in it's almost as if something is spinning behind it knock Ng the pedal up and down. Any ideas as to what it could be? I would be grateful. Many thanks in advance.