The term 'CERTAIN TANKER' can be broken down into two crossword solutions: OILER (5 letters) and TANKER (7 letters). An Oiler is a person who works on a ship, typically in the engine room, and is responsible for lubricating and maintaining the machinery. A TANKER is a large ship designed to transport liquids or gases in bulk, such as oil, gasoline, and liquefied natural gas. Together, a Certain TANKER would refer to a specific type of TANKER that carries oil or other petroleum products.