The term 'Mystery Item' can be solved by the crossword clues 'UFO' (3 letters) and 'CLUE' (4 letters). The acronym UFO stands for Unidentified Flying Object, which is a phenomenon that has been reported since ancient times. It is usually described as an object or light seen in the sky that cannot be identified or explained. CLUE is an acronym for Clues, which are pieces of information used to help solve a mystery or puzzle.