Possible Clues:

• Complete reversal of direction
• You might get a ticket for one
• Radical maneuver
• What you might have to make if your GPS messes up
• It'll take you back
• Major change of course, but without first vessel (1-4) (WARNING: Two answers in this special 2500th puzzle require numbers as well as letters. The figure zero must be entered as a capital O.)
• Complete change of mind
• Complete reversal of policy
• About-face of a sort
• Hard thing to do in a jam