Lyrics: Robert Hunter
Music: Bill Payne
This response by Bill Payne in an interview with Blair Jackson makes it sounds as if this is the title of a Payne/Hunter song. I haven't found any indication that it has yet been played by Little Feat or by Bill Payne solo:
"Originally, Robert sent some lyrics which Paul and I both looked at, and I think Paul sent him some music and wanted to make a few changes with Hunter’s lyrics, which [Hunter] was not agreeable to. So that didn’t work out. Then I wrote this one song, “What Are You Waiting For,” and it turned out pretty cool, so Hunter and I were off and running. That one’s not on the record. 'Rooster Rag' was one of the first ones that came down the pike."There are almost identical quotes in other Bill Payne interviews but with the title of the song given as "Waiting For The Rain". I don't know whether these were different songs or different titles for the same song (though ASCAP has a registration for "Waiting For The Rain" with music by Bill Payne, but not for "What Are You Waiting For").