Without digging into this I'd say you'd have to make an Applescript that selects all the tracks in the playlist and does the equivalent of hitting the delete key - meaning you'd have to "script the interface"
I'm saying that because in the dictionary I don't see anything in the Applescript dictionary for removing a track from a playlist. Just adding....
And a quick look on Doug's Applescripts didn't show a way to do this either. Nor Automator. Unless I'm missing it.
Scripting the interface is fine, but not as good as if there were a way to directly delete the tracks.