Found in Helvetia: rather small crown (5)
I believe the answer is:
tiara
'small crown' is the definition.
(I've seen this before)
'found in helvetia rather' is the wordplay.
'found in' indicates a hidden word.
'TIARA' is hidden within 'helvetia rather'.
(Other definitions for tiara that I've seen before include "pope may have been topped by one" , "Jewelled coronet" , "Great delight" , "Ornamental head band" , "Decorative headgear" .)