Does Clefairy for example also receive reduced damage because of friend guard, or is it just for its partner? I might just be dumb but I can’t tell if “allies” includes itself. Thank you!
No. "Allies" refers to your friend Pokémon. So Pokémon that are your "allies" receive reduced damage in double battles by opponents and allies too by 25%. The Pokémon having that ability is not affected.