This is a "themed ladder" - the asterisk denotes the themed words. In this ladder, you either substitute one letter for two, or two letters for one, according to the instructions.
All of the clues in this ladder were taken from New York Times crosswords from the past 15 years. You want to get really good at word puzzles? Do the NY Times crossword! Mondays are the easiest and they get harder each day. Start at your level and work up. These are Monday/Tuesday type clues.