[I’m about to speak …]

The answer to this crossword clue is ‘AHEM’. The clue hints at a preamble that some people use before speaking, which is ‘ahem’. This is often done to draw attention or signal that the speaker is about to start speaking. ‘Ahem’ is a short, sharp cough-like sound, and it is usually followed by something important or relevant that the speaker wants to say. Therefore, the answer to this crossword clue is ‘ahem’.