RenderTexture doesn't get cleared and camera just adds to it

I applied a render texture to one of my cameras to render on top of the other.
The problem is that it looks like it doesn’t clear the texture before the camera adds the new render to it. As a result I get some weird ink-flow-like effect witch is not what I’m after.

The first image is what I should get, it is just an editor screenshot prior to runtime.

The second image though is during runtime when I moved the camera around a bit. It added up to it, but ultimately didn’t clear the texture beforehand.
How to set this up right?

Change your blur cam’s clear flags to solid color with an alpha of 0. it solves the issue.