Mortarboard attachment (6)
I believe the answer is:
tassel
'mortarboard attachment' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tassel that I've seen before include "Grapefruit and tangerine hybrid" , "Decorative bunch of cords" , "Decorative hanging tuft" , "Hanging tuft of threads" , "male hawk" .)