Possible Clues:

• Local line running through Rochester
• Dart throwers step up to it
• Darts players step up to it
• Phil Taylor often steps up to it
• Line from which darts are thrown
• Darts' line
• Martin Adams often steps up to it
• Man, the one in command on the front line
• Local restriction for missile launcher?
• Stand behind one aiming to put points on board