What is the best way to rid a combination St. Augustine/fescue lawn of clover. It is taking over.

IMO you need to add nitrogen to your lawn. When clover is heavily present (especially white clover) it is often sign of lack of nitrogen available in the soil. Clover's job is to fix the nitrogen in the soil by extracting it from the air and then making it available for plants uptake.

I can't offer an answer, because I don't encourage or discourage the clover in my parkway. The clover shares space with a mixture of Bermuda and St. Augustine. The results, for me, are visually pleasing. For whatever reason(s), in the main yard areas where I have Tall Fescue in the mix, I don't have any clover.

Post what you decide to do and the results.