Jewelled headdress (5)
I believe the answer is:
tiara
'jewelled headdress' is the definition.
(I know that tiara is a type of jewelled headdress)
This is all the clue.
(Other definitions for tiara that I've seen before include "Small crown" , "special headgear" , "Pope's triple-tiered crown" , "Jewelled crescent-shaped headdress" , "Women's head ornament" .)