Possible Clues:

• One missing coal fires for a change in the open
• Half-hearted repositioning of forces in the open
• 'eadlight caught liegeman going back inside - or not?
• Located outdoors
• Flares are set off by the house, in the open
• Five hundred from Alfred's company like a picnic
• On the outside gangster takes painting
• Alf can come up with a score and it's all in the open
• I will avoid various coal-fires out of doors
• Unusual scale for outside location