Possible Clues:

• Obstacle that limits success — what's that? The government!
• For administrators, what can divide a little from the lot
• Screen welcomes box-office success from end of June to end of March in Dublin suburb
• Civil service barrier restricts success, what?
• Street between Pall Mall and Northumberland Avenue, especially in Monopoly
• London thoroughfare synonymous with British government
• Government in spotless country house?
• British government a little bit sorry? The lot of them!
• London street; the British government or civil service
• Street in Westminster in which many government offices are located