Actually, leaving it on the yeast will clean up that flavor quicker. The acetaldehyde is an intermediate flavor the yeast create while converting the sugars. Once fermentation is complete, the yeast then start to work on the intermediate esters and clean them up. Racking to secondary takes the beer away from a lot of this working yeast, so it takes the little yeast left longer to do the job.My first four beers, all extract LME/DME kits, had significant acetaldehyde "green apple" flavors. By the fourth batch, i learned if I racked to asecondary and let it sit in the closet, it cleaned up. It took a month, but I finally had drinkable beer.