Possible Clues:

• Disgusting place at the front, clear at the back
• Really rotten and foul-smelling
• High when set free
• It's badly in need of a wash with that much back up there
• Malodorously decaying
• Fetid
• Bad smelling, rotting
• Decomposed, rotting
• That dirt back up there makes it all quite disgusting
• How the top of 1 across will go bad if you get rid of it