Possible Clues:

• By the end of December shortly make a speech, but that will not make it plain
• Spruce up last month's lecture
• Pin medals on, to make look prettier
• At the end of the month it will not make it plain to make a speech like that
• Doctor created the first organic paint
• Last month to make speech and confer award
• Make a speech at the end of last month to add some colour to it
• Beautify by additions
• 'Adorn, beautify (8)'
• Give an order -- to paint?