The term 'water tester' can be broken down into two crossword solutions: TOE (3 letters) and BIGTOE (6 letters). A water tester is a professional who tests the quality of water, usually for safety or environmental reasons. They use specialized equipment to measure the levels of various contaminants in the water, such as bacteria, chemicals, and metals. The TOE solution could refer to the testing process itself, while the BIGTOE solution could refer to the importance of the job, as it is essential to ensure that the water is safe for human consumption.