As a detective, my first step in solving the mystery of the crossword clue ‘Bert of Cowardly Lion fame‘ would be to analyze the context of the clue. The clue refers to ‘Cowardly Lion fame‘, which immediately suggests the classic movie ‘The Wizard of Oz‘. Then, my next step would be to identify the characters from the movie that fit the description given in the clue. In the movie, Bert Lahr played the character of the Cowardly Lion. It’s also important to note that ‘Bert‘ is a common nickname for ‘Albert‘, and ‘Lahr‘ is a rare enough surname to narrow down the possibilities of who the clue refers to. With this in mind, I would confidently fill in the answer ‘LAHR‘ in the crossword. The thought process of analyzing context and identifying relevant information is crucial in solving crossword clue mysteries.