Possible Clues:

• Self-indulgent month leads to a depression
• Declining a cent with the dead
• A duke, outwardly proper, is immoral
• Father may be back in decent surroundings in a rather indecent way
• Last month a hollow appeared decaying
• Self-indulgent act ended careers
• Some years with conservation group that's corrupt
• Luxuriously self-indulgent
• Decanted, being corrupt and immoral
• In decline these days, but outwardly proper