The top track is the original waveform. The lower track has the phase (technically speaking polarity, but that's a geek thing

) flipped. To do this:
1. Insert Channel Tools into the track with the clip you want to flip.
2. In the Channel Tools UI, check the Phase button for both channels.
3. Click on the clip you want to flip (this selects it).
4. Choose Process > Apply Effect > Audio Effects.
This will modify the waveform (hence the term "destructive") and flip the polarity.
I do think "click on the clip you want to flip" may have lyrical possibilities