While there may be some background research in evaluating deals, "clearing title" doesn't happen until the title company is ready to close your transaction.
Obtaining and reviewing a title search is not the end of clearing title. It may give you a good idea of what's going on with a property, but that's certainly not the end of it. Let's say you identify a target and buy a title search from some online-only search company (ptooey). The title report identifies 2 potential liens -- a mortgage and a judgment. In order to clear title you'll need more than written payoff statements from both lienholders (oh, the seller hasn't paid his mortgage in 6 months -- he didn't mention that!) ... you'll also need a tax cert, water bills and any other payoffs potentially affecting title. Some sellers are clueless as to what they really owe to get out of a property.
The best way to "clear title" as a buyer is to avoid getting yourself in a title mess by wholesaling a deal that can't close. You do this by requiring (as others have mentioned) clear and marketable title from you seller as a prerequisite. The right contract forms are invaluable in your trade.