Next to World 5-5 is a small pile of rocks. Move them to reveal a pipe that takes you to this level. With a Fire Flower, Cat Power-Up, Boomerang, or Tanooki Suit you can hit the Goomba Tower and defeat the Fire Bro easily. Otherwise, you need to jump from tower to tower until you are high enough to bounce off the top foe all the way. It’s much easier to chop down the tree then it is to climb to the top of it.
Claim the Green Star and head over to another bonus level.