1920s design (3,4)
I believe the answer is:
art deco
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">1920s design</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for art deco that I've seen before include "Style of design popular in the 1920s and 1930s" , "Old style" , "Style of 1920s/30s" , "pre-war style" , "Highly geometric style" .)