Primal Clash Beedrill

[JimmerJammer]

Primal Clash Beedrill's attack, Allergic Shock, states During your next turn, if the Defending Pokémon is damaged by an attack, it is Knocked Out. If Beedrill attacks with Allergic Shock to the Active/Defending Pokemon (we'll say it's Mewtwo), then Mewtwo retreats, will an attack on your next turn that is able to do damage to a benched Pokemon knock Mewtwo out or if Mewtwo is Lysandre'd to the active position and damage dealt? Based on the definition of "Defending Pokemon", would not Mewtwo be the defending Pokemon still in either situation? Or, is it considered an effect, in which case when Mewtwo retreats the effect is removed and Allergic Shock proves to have been a wasted attack?

 

[PokePop]

All attack effects are removed when a Pokemon retreats to the bench. ALL attack effects.
Any exceptions have to be explicitly stated, and that is not the case here.
Going to the bench removes the effect.