Use opacity without showing what's behind, is there a way?

[Edu Borrell]

Is there a way to make the same effect (whit opacity) without affecting other layers?

I want to make the hat like it's solid, but when I apply opacity in the layer, obviously it shows what's behind. Does anyone know a way to make the same effect but respecting the order layer, maybe whit some fusion mode or effect? Or do I just have to cut the other elements?

[Rick Gerard]

Unfortunately, your screenshot does not show us anything that you have done to the comp. It looks like you have some kind of layer or mask on a layer and you have reduced the opacity. I assume you are trying to create some kind of blinking eye effect. That is usually done with an animated mask or a track matte. 

Please describe your workflow in detail and include a screenshot of the entire timeline with the modified properties of all problem layers revealed. You can reveal any changes you have made to any layer by selecting the layer and pressing the "u" key twice. A little note about your experience level with AE would also help.

[Edu Borrell]

I did nothing special in this layer, just set the opacity to 0-100%. My "problem" is that I don't want the overlapping effect between the hat and the face. I would like the hat to be solid and the top of the head not to be seen. A clean cut with nothing behind.

The head (the marked red area) will not be visible while the opacity is being established. That it be clearly understood that the hat is on top of the head.

[Edu Borrell]

I'll define my experience level as intermediate