The crossword solution for the term 'INNER STARTER' is ENDO, which is a four-letter word. ENDO is a prefix derived from the Greek word 'endon', meaning 'WITHIN'. It is commonly used in medical terminology to refer to something that is located inside or WITHIN the body. For example, endoscopy is a procedure used to look inside the body, and endocarditis is an inflammation of the inner lining of the heart. ENDO is also used in other contexts, such as in engineering, where it refers to a motor or engine that is located inside a device.