Depends which bit, if you're talking about the inner basket, check your main shaft is not loose in the bearing, or the bearing in the case. A knackered inner basket circlip can also pop out of the groove - all of your spring pressure is against it when the clutch is pulled. In that case the whole shaft or clutch assembly can move in and out, can happen.
The outer basket sits between a washer on the step in the shaft, and other washers behind the circlip on the outside. It is meant to have a little clearance since it needs to spin on the shaft when the clutch is in, but not much. No doubt there is an official clearance specified somewhere. The washers allow for alignment with the front sprocket but if they've been mixed up or omitted you can end up with too much float on the outer basket and/or alignment issues.
HTH
SteveB
