Can a Gen 1 Clefable use its Metronome attack to copy the defending pokemons move if the Clefable has the energy to do so but the defending pokemon does not have the energy themselves to use the attack?
If you're talking about Jungle set Clefable, Metronome copies the attack regardless of Energy requirements or attachments on the defending Pokemon. As an example, Metronome is the ultimate counter to say, Rocket Zapdos; check it out.