Possible Clues:

• Business that requires union membership before hiring
• All union members finished business for the day
• 'The shutters are up, save for the union (6,4)'
• Union arrangement ended quiet operation
• Shut down business - only the unions were taken in
• Ceased trading where union holds sway
• Where union membership is required
• Contemporary village feature for union members only
• Union restriction less often seen nowadays on a Sunday
• Union bastion holds scope for redevelopment