It basically means 'easy win'. I guess it is meant to mean someone clapping at the end of a match because it was so easy to win. Or the clap means you clapped the enemies' cheeks (again, meaning EZ). It's like saying GG EZ basically.

What is EZ clap in twitch?

The Brief: Ezclap is a Twitch emote that means victory or a win was achieved easily. It is represented by Pepe wearing sunglasses and a black jacket.

What does clap mean in gaming?

to mean being destroyed or obliterated, most often in video games or hyperbolically, in sports. Getting clapped goes beyond taking an L.