The clutch is not a difficult part so best is to first dismantle it by removing the 3 bolts and check the condition of steel plate surfaces and on the extend the clutch plates have worn into their slots.
The clutch sprocket usually has quite some play, even when the clutch is not disengaged. That is nothing to worry about, just part of the design.
You have to check if the central nut is still correctly fastened.
If that is loose you will also have some trouble in disengaging the clutch.
Its not uncommon for this nut to come loose. Adjustment of the cable will only temporarily solve the problem.
When you install the clutch plates, put some oil on them.
If you run with oil in the chain case you don't need to add much.
If you run a dry chaincase, lubricate the clutch a bit regularly.
The rollers in the sprocket drum do need some lubrication.
Before you pull it apart do this: pull in the clutch lever and operate the kickstart. If the engine turns over normally then the plates are sticking. If it slips against compression then its probably OK.
