Design style (3,4)
I believe the answer is:
art deco
'design style' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for art deco that I've seen before include "Redcoat (anag) -- inter-war design style" , "modern style" , "Architecture and design movement of the 1920s and 30s" , "Style popular in the 1920s and '30s" , "Style of design popular in the 1920s and 1930s" .)