Possible Clues:

• Circular crumb put in mouth
• Roundabout that�s out of this world!
• Relating to planet's motion
• Of planetary paths
• Of road, circling a town
• Course not much spoken about, like the M25
• Like the M25
• Getting around this, or part of a half-century
• Gold coin — a sovereign? — in circulation
• Got around the whole of it, or part of a half-century