The term BRAINS BELONG TO IT can be solved by the crossword clue MENSA, which is a five-letter word. MENSA is an international organization for people with high IQs. It was founded in 1946 in Oxford, England, and is now open to anyone who scores in the top 2% of any standardized intelligence test. Therefore, the answer to the crossword clue is MENSA, and the complete sentence is 'Brains belong to Mensa.'