Quinceañera accessory (5)
I believe the answer is:
tiara
'quinceanera accessory' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tiara that I've seen before include "Ornamental headpiece" , "Decorative headband" , "Jewelled coronet" , "Jewelled crescent-shaped headdress" , "Woman's crescent-shaped ornamental headdress" .)