Good morning all.
Clutch centre nuts can be a pain, if it wont undo using the bike in gear trick, have a new nut to hand, & with the bike in gear, apply a little 'percussive adjustment' to the old nut using a cold chisel & hammer. Often the 'shock' will easily loosen a seemingly tight nut.
Be careful you don't slip, or you may well end up needing a new clutch centre.
Cheers.
P.S. I cheat, for I have an air driven impact wrench
