Wow, delightful ornamental feature (7)
I believe the answer is:
cornice
'ornamental feature' is the definition.
'wow delightful' is the wordplay.
'wow' becomes 'cor'.
'delightful' becomes 'nice'.
'cor'+'nice'='CORNICE'
(Other definitions for cornice that I've seen before include "Moulding along top of building" , "Overhanging ledge of frozen snow" , "decorative part of room" , "Crane-fly" , "decorative feature" .)