The art of home improvement? Si! (8,6)
I believe the answer is:
interior design
This could be a double definition.
'the art of home improvement?' is the first definition.
'si' is the second definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
(Other definitions for interior design that I've seen before include "Decoration and furnishings for rooms" , "Planning for home" .)