Possible Clues:

• Permitted at last to have migrated, perhaps
• How 17 across got 19 across at last
• Passed through the oesophagus as part of eating or drinking
• Thus brick structure can be installed within a day, it's believed
• Permitted at last to have got it down
• The bird begins to have been permitted at last
• Got it down with permission at last
• Gulped
• Perhaps swiftly got it down
• South side of a building due to be bought