Clear flags in camera and render texture problem

I’m trying to capture camera to render texture and use that in quad to show camera output.
I’m having issues with clearing the texture by transparency.
When I have the camera clear flags set solid color it does clear the texture properly. But if I set it to depth only and move the plane with dots in front of camera up and down it gets burned into the texture and texture has black backround.
I need to get transparent properly cleared render texture out of the camera.
What am I doing wrong?

I show render texture on quad using unlit/transparent (or any other alpha shader). it always draws black background.

thnaks for help

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Setting clear flags to color and choosing transparent color did it ;o( I don;t know how I could miss this I tried everything before… never mind, solved…