Possible Clues:

• Hangs down, though no not much at the turn
• Let it hang up around the start of 18 across
• Mortar board attachment plastered slates
• Not so much at the turn does it hang
• It's hanging not so much at the turn
• Mortarboard doodad
• Drapery elaborations
• Part of maize plant rejected for fear that it contains arsenic
• Graduation-cap ornament
• Set of threads?