Please add something like a k/d!

I mean:

won defenses + won attacks
divided by
lost defenses + lost attacks

Like in cod or other egoshooters. I would call it W/L (Won/Lost) or something.

What do u think about it?

This falls under the category of "name and shame" and Supercell doesn't implement such ideas. They don't want anyone to be included/excluded to/from a clan simply based on how their historical W/L rating is.