Possible Clues:

• Mechanical solar system model
• Moving mechanical model alternatively concerning railway
• Planetarium that illustrates the positions and motions of bodies in the solar system
• Clockwork model that takes a lot of space
• Unexpected error over variable astronomical model
• Model of solar system
• Doubler, perhaps, in a setting of yore for a heavenly model
• Politician takes time off to admit blunder about working model
• How Roy is about to err in such a planetary manner
• Err, Roy, on the side of a model of the solar system