I see nothing wrong with you current moveset. One thing I would change is the Nature and possibly the EVs. I would change the Nature to Bold to maximize both Defenses. Also, if you want to keep the Special Defense raising Nature, I would suggest Calm instead. I say this because every stat Point counts, especially in Speed. You currently aren't using your Attack stat, so I would recommend using this nature instead if you want to raise your Special Defense, but I would recommend Bold to maximize your defenses though. And from experience in the Battle Tower, I would definitely keep Thunder Wave. Since there are only 3 Pokemon in this format and the AI rarely switches out, I believe Thunder Wave is better. It has an overall better utility in my opinion to give Clefable more bulk as well as to maximize Clefable's potential to stall. This is my opinion for your moveset, but it is entirely your choice to accept it or not. I do think that Bold is better, but you can choose Calm if you want.
I hope this helps!