Possible Clues:

• Slowly decay
• His job is to cast waste away
• Decay gradually
• Decay and disintegrate
• Opinion-influencer to crumble?
• Somebody making blancmange or crumble
• That's a grave way to decay
• Decay
• What the castor will do with what John Brown's body will do
• What the 12 across will do to get things in shape, perhaps