The crossword solution for the term LEAD-IN TO ZONE is EURO, which is a four letter word. Euro is the official currency of the European Union and is used by 19 of its member states. It is also the second most traded currency in the world after the US dollar. The euro is used as a lead-in to zone when referring to the Eurozone, which is an economic and monetary union of 19 EU member states that have adopted the euro as their common currency.