I'm not quite sure what you mean by throat clearing. Based on the title, however, I'm assuming you mean introductory info-dumps, and am writing my answer based on that.
There is no hard rule for this that I know. Meaning, I'm not sure there's any official limit to how many introductory remarks you can add. The main concern is holding your reader's interest.
However, I would advise you to add as little introductory details as possible. Take out all the details that don't move the story forward, especially those that aren't relevant at the moment. Add those details later on, when they do become relevant. Try to add them as part of the story, and not as "throat clearing".
I'd also advise you to make sure the "throat clearing" doesn't make the story boring. Read over your interview and revise it until you find it interesting. Then, get a few people to read over your draft and ask them if they think you added too many introductory remarks. This is the best way to know if your added too many details, since your main concern is holding your readers' interest. If your readers find it interesting, you're good to go. Otherwise, revise your interview until they do.