Something headily beautiful (5)
I believe the answer is:
tiara
I'm afraid I can't even guess how this answer relates to the clue.
Can you help me to learn more?
(Other definitions for tiara that I've seen before include "pope may have been topped by one" , "Jewelled head wear" , "It bejewels" , "Jewelled crescent-shaped headdress" , "Pope's triple crown" .)