The crossword solution for the term 'Find by Investigation' is 'TRACE.' This term is often used in the context of criminal investigations, where law enforcement officers are tasked with tracing the source of a crime or finding evidence that can lead to the identification of a suspect. It can also be used in other contexts, such as when a person is trying to find out the origin of a product or uncover the truth about a particular event. In all cases, it involves a thorough investigation and analysis of available information.