I won't say Clefairy really belongs in Bottom, but after thinking through things, I think Low is a perfect fit for it. It's one of the more acceptable fillers, while it's not as good as one like Sawk or Bouffalant, Clefable does the job fine if you want something that can learn a good range of offenses. Fire Blast, Ice Beam, Thunderbolt, Facade, Assist Power; they're all acceptable options for Clefable. The wide TM movepool is enough to convince me that this guy isn't meant for Bottom, since it very obviously can do something (unlike say ditto).
To put it, Clefable is essentially a 'jack-of-all-trades, master of none'. It's capable of using quite the fair bit of things, but it lacks really legitimate firepower behind it compared to others. Return nuking? Zangoose and Bouffalant does it better. Boltbeam? Starmie is probably the guy to go to. Fire Blast? it's shit in elite four ;_;. It's versatile, yes, but it's not something that's very good for endgame. I'd probably disagree with Low at this point, and Clefable would be a perfect fit for any tier between Low and Bottom, but considering such a tier doesn't exist (limbo tiers aren't permanent) I'd say Low.
of course if we bring in stoutland and his elemental fangs/intimidate utility... :(