if you mean the head of a spring bolt broke, snapped or sheared off??
take the rest of the bolts off (lefty loosey) and pull the outer plate and all of the clutch friction plates and steel pates off as a whole unit and stick a zip tie through one of the holes and around all the plates and sinche it up so you dont loose order of the assembly.
then get the center clutch hub nut off and the clutch hub out at this piont you should take it to a machine shop and have them remove the bolt, if it where me I could do it myself with a new drill bit and an easyout, but I have no idea of your skill sets.