Doublade as a check on Ghost.
Being part Steel and having decent bulk with Eviolite, Doublade is able to take on Clefable easily unless it's a Flamethrower variant.
Gengar as a check on Ghost.
Gengar is a very hard-hitting part Poison-type which can take on Clefable even with Special Defense boosts.
Mega-Scizor as a check on Bug.
Mega Scizor is part Steel and is able to take on Clefable with no problems unless it's carrying a Fire-type move.
Durant as a check on Bug.
It's not always a safe switch in due to the possibility of Flamethrower, but if it's already inside, it's gonna get a kill with Iron Head.
Magnezone as a counter on Electric.
Magnezone's Steel typing and bulk allow it to take on Clefable without any issues as it's also immune to Thunder Wave, a move Clefable often uses to cripple the opponent.
Heatran as a counter on Fire.
Heatran has a 4x resistance against Clefable's Fairy STAB type and is immune to Clefable's other common attack, Flamethrower. That plus its great Special Defense allow it to counter Clefable even when it is at +6.
Empoleon as a counter on Water.
With amazing Special Defense, Steel typing and access to Roar, there's not much Clefable can do in front of Empoleon.
Bisharp as a check on Dark.
Bisharp's really high Attack stat and Steel typing allow it to OHKO Clefable with Iron Head; however, it can't switch in so easily, as Moonblast and Flamethrower still do a good amount of damage.
Drapion as a counter on Poison.
It's Poison typing, decent bulk, and access to Taunt allow it to be a reliable answer to Clefable on Dark.
Mega Aggron as a counter on Rock.
Mega Aggron's Steel typing and amazing bulk allow it to deal with Clefable easily, as it doesn't even fear a Flamethrower due to its Filter ability.
Jirachi as a counter on Psychic.
Jirachi's great bulk, Steel typing, and the high chance to flinch with Iron Head due to its Serene Grace ability allow it to deal with Clefable quite easily.
Metagross as a counter on Psychic.
The great bulk and Steel typing that Metagross possesses makes it a reliable answer to Clefable which can't do much back even with Flamethrower.
Mega-Venusaur as a counter on Grass.
Mega Venusaur's amazing bulk and Poison typing allow it to take on Clefable without too many issues.
Amoonguss as a counter on Grass.
With great bulk, Poison typing, and access to Spore and Clear Smog, Amoonguss deals with Clefable pretty well.
Ferrothorn as a check on Grass.
Being part Steel and having great bulk, Ferrothorn checks Clefable pretty well unless it's carrying Flamethrower.
Cobalion as a check on Fighting.
Cobalion's Steel typing allows it to take neutral damage from Clefable's STAB Moonblast and deal serious damage to it with a STAB Steel-type move.
Toxicroak as a check on Fighting.
Toxicroak's Poison typing allows it to take neutral damage from Clefable's Moonblast and take it out with a Poison-type move.