Belfries designed to incorporate a type of sculpture (3,6)
I believe the answer is:
bas relief
'type of sculpture' is the definition.
'belfries designed to incorporate a' is the wordplay.
'designed' indicates anagramming the letters (designed with the letters).
'to incorporate' is an insertion indicator.
'belfries' with letters rearranged gives 'bsrelief'.
'bsrelief' enclosing 'a' is 'BAS-RELIEF'.
(Other definitions for bas relief that I've seen before include "work of art" , "Moore may have produced this" , "Sculpture" , "less outstanding work" , "projected figure" .)