Britney Spears is back with a video for ''Womanizer,'' the first single from her next CD, Circus (out Dec. 2). The good news: It's not a hot mess. But is it the beginning of an honest-to-God comeback? It looks promising. Given all her personal and professional missteps, Britney has a lot to atone for, and that's going to take more than one good clip. At least ''Womanizer'' hints she's leaving behind the splotchy, Frappuccino-guzzling train wreck who dominated headlines for so long. The dancing is stiff and minimal, a disappointment since her moves are her strong suit. But this is a welcome return to the Britney we love gorgeous, gyrating, greased up, and gamely playing the vamp. It's a good start. And besides, if we could pardon Mariah for Glitter...well, anything's possible, right?