The term 'deepen, as a canal' can be solved by the crossword solution 'DREDGE, ' which is a six-letter word. Dredging is a process of excavation and removal of sediment from the bottom of a body of water, such as a canal, to deepen it and make it more navigable. This process is often used to improve navigation channels, or to create new ones. It is also used to remove pollutants from the water, and to restore habitats for aquatic life.