The term 'No PAIN, No Gain' is a popular phrase used to emphasize that hard work and effort are necessary in order to achieve success. It implies that one must endure some level of difficulty or discomfort in order to reach their goals. The crossword solution for this phrase is 'PAIN', which is a four-letter word. This phrase has been used in many contexts, from sports to business, to motivate people to push themselves and strive for excellence.