Jewelled headband (5)
I believe the answer is:
tiara
'jewelled headband' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for tiara that I've seen before include "Crescent-shaped headdrsss or Pope's diadem" , "Ornamental crescent-shaped headdress or Pope's diadem" , "Jewelled headwear" , "Jewelled headpiece" , "Item of jewellery" .)