When you win a Florida tax deed sale, it will usually clear out most mortgages, meaning the mortgage would no longer encumber the property after the tax deed is issued. The big exception is notice. If the mortgage holder was not properly found, listed, and noticed through the tax deed process, then that can create a serious title issue and the mortgage holder may still have rights that need to be dealt with.
Tax deed auctions also do not automatically clear every government related lien or encumbrance. Things like IRS liens, state liens, county liens, city liens, municipal liens, special assessments, utility liens, and code enforcement violations can survive or create problems after the sale. This is why you cannot just assume the opening bid or auction price is your only risk. You need to research all recorded and municipal issues before bidding.
You also do not get what most people would call a clean title just because you won the auction. You get a tax deed, but that does not mean a title company will insure it or that a regular buyer or lender will accept it. In most cases, you will need a quiet title action or another title clearing process before you have clean, marketable, and insurable title. That is why tax deed investors should always do title research before they bid, not after they win.