The part you mention is the drive clutch. If it will not turn, it is either bad or the drive pulley under the transmission is binding. To find out which, simply slip off the belt from the pulleys and try turning the center transmission pulley by hand in both directions. There should be no binding in either one. If it is difficult to turn, the transmission or the tub bearing may have to be replaced, or something may have washed over the top of the tub and is binding it to the outer tub. If it does turn smoothly, the clutch is a replaceable part also, just less expensive.