To do something you've been putting off. To do something you don't want to do.
I've been cleaning the house for hours, and it's spotless. Now it's time to rescue the snakes and clean up the puke in the bathroom.
Reference: from the movie "Pee Wee's Big Adventure." The scene wherein Pee Wee Herman is rescuing animals from the burning pet shop. He does not like snakes, and rescues them last after every animal is safe, with a grimace on his face while screaming.