Found in Croatia, rare crown (5)
I believe the answer is:
tiara
'crown' is the definition.
(I know that tiara is a type of crown)
'found in croatia rare' is the wordplay.
'found in' says the answer is hidden in the clue.
'TIARA' can be found hidden inside 'croatia rare'.
(Other definitions for tiara that I've seen before include "Jewelled head band" , "Jewelled crescent-shaped headdress" , "Woman's head ornament" , "Jewelled headwear" , "Ornamental headpiece" .)