Sparkly headpiece (5)
I believe the answer is:
tiara
'sparkly headpiece' 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 "Jewelled head band" , "Jewelled headwear" , "It bejewels" , "Small crown" , "it goes to one's head!" .)