If you are using the iPhone app, clear the search box by tapping on X to the right of the search term.
If you are using Safari or another browser, tap on the last icon to the right of the search field, a circle with a small down arrow inside. There is a Clear Map option. Tap that option (not the small x icon, which would make sense, but somewhere in the middle of that line).
If you are using some other app, you'll need to specify.