Gday!
What I’d personally do, is take the entire music clip into the multitrack view, and split the clip so that you have three sections… the music before you want it slowed down, the part you want slowed down, and the music after the slowed down part.
Create uniqe copies of these 3 clips (right click on them), and then slow down your middle clip the way you want it (dooo riii meee, haha). Arrange the clips in the multitrack view so it’s all lined up and sounds good, and create a mixdown!
djfrogi.tk