The Clue Ad ___: Ogilvy and Mather, say
The Answer AGENCY
The clue "Ad ___: Ogilvy and Mather, say" refers to a type of business that creates advertisements. Ogilvy and Mather is a well-known advertising agency, which fits perfectly with the word "agency." In this context, "Ad agency" is a common term used to describe companies that specialize in marketing and advertising. Therefore, "agency" is the correct answer to the crossword clue.