Window ornamentation (7)
I believe the answer is:
'window ornamentation' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for tracery that I've seen before include "Fine, decorative pattern" , "Fine stone openwork" , "Thin ribs of e.g. Gothic window" , "Fine open stonework" , "Ornamental stone work" .)