In Croatia, rarely-worn headdress (5)
I believe the answer is:
tiara
'headdress' is the definition.
(tiara is a kind of headdress)
'in croatia rarely-worn' is the wordplay.
'in' indicates a hidden word.
'TIARA' can be found hidden inside 'croatia rarely worn'.
(Other definitions for tiara that I've seen before include "Ornamental headpiece" , "Jewelled headband" , "High diadem" , "Jewelled crescent-shaped headdress" , "Women's head ornament" .)