Why do I have a white background when I cut a layer ?

[FlameAndCo]

Hi, today I used gimp for the first time in a while, and for some reason when I try to cut a part of a layer, instead of just making the part disappearing like it used to, it turns the part white.
Left is what I want to do, and what I was used to, right is what I'm getting.

Anyone knows why it does that and how to fix it ?

[tmanni]

Because the layer you cut does not have an alpha channel (so the cut is filled by the background color).
Right-click on the layer in the layers list to open the contextual menu and choose: Add Alpha Channel