How to bring a clip to front or back in FCP 11 ?

I have a horizontal footage which I try to rearrange in vertical (1080 x 1920) in FCP.

In some locations, I am using 3 clips repositioned one above the other. However, in order to fill all the black space, I need to resize (transform) each clip. For one in the middle, because of the resizing the one at the top, I end up with a black zone over part of the middle clip.

Isn't there a simple way (such as what a photo editor can do with pictures) to have this middle clip ''at the front'' of the resized top clip ?

Been searching for such a feature for over an hour now...