The crossword solution for the term CHECK, AS A FLOW is STEM. The term 'STEM' is used to describe the main trunk of a plant or tree, which provides support and structure for the rest of the plant. In this context, it can also be used to refer to the main source of a flow, such as a river or stream. Checking the STEM of a flow can help to identify any potential problems or issues that may be affecting the flow.