What does the cryptic crossword clue "Way to address lady in Mothers' Union? (5)" mean?

The wordplay uses a charade (building blocks). MA (synonym="MA") + DAM (synonym="DAM") = MADAM The answer is MADAM.

Way to address lady in Mothers' Union? (5)

Times Cryptic #28651 | 18 Across | 2023-07-10 flower