Complex sentence: The landmark is described on a clue sheet, and often is not a feature on the map; e.g., the landmark might be a tree of a noted species and size, perhaps marked in some way for the competition.
Split into simpler sentences: The landmark is described on a clue sheet, and often is not a feature on the map. E.g., the landmark is a tree of a noted species and size, perhaps marked in some way for the competition.