The line scans like this:
/ x x / x x / x x / x x / x /
Simple and clean is the way that you're making me feel tonight
so one way to describe this would be “catalectic dactylic hexameter with a trochee in the penultimate foot”. But really the song isn’t regular enough in its rhythm for that kind of prosodic description to be useful. What you might say instead is that the song is mostly stressed on every second syllable:
/ x / x /
When you walk away
/ x / x /
You don't hear me say
/ x / x / x
Please O baby don't go
but then switches to being stressed on every third syllable for this line, making it stand out from the rest, appropriately enough, as it is delivering the theme and title of the song.