A form of art (9)
I believe the answer is:
sculpture
I believe this clue is a double definition.
'a form' is the first definition.
(sculpture is a kind of form)
'art' is the second definition.
(sculpture is a kind of art)
'of' is the link.
(Other definitions for sculpture that I've seen before include "artistic work" , "Artwork produced by carving, moulding etc" , "Art in three dimensions" , "Plastic art" , "Carving art" .)