The term 'well-versed in' can be defined by the crossword solutions of 'FLUENT, ' 'ADEPT, ' and 'UPON.' FLUENT means to be able to speak or write a language with ease and confidence. ADEPT means to be highly skilled or proficient at something. UPON means to be in a position or state after something has happened. Therefore, the term 'well-versed in' can be interpreted as having a high level of skill or proficiency in a particular area, as well as being able to speak or write about it confidently.