Decorative style (3,4)
I believe the answer is:
art deco
'decorative style' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for art deco that I've seen before include "Nineteen twenty's and thirties style" , "Architecture and design movement of the 1930s" , "Style of decorative art popular in 1920s and 1930s" , "1920s and 1930s ornamental style" , "Style characterised by bold geometric shapes" .)