The term 'FASHIONABLE, IN THE 60's' can be summarized by the crossword solution MOD, which is a three-letter acronym for 'Modernism'. MOD was a popular fashion style IN the 1960s, characterized by bright colors, geometric patterns, and a focus on youth culture. It was a reaction to the more conservative styles of the 1950s, and was embraced by young people who wanted to express themselves through their clothing.