Rated new company's architectural style (3,4)
I believe the answer is:
art deco
'architectural style' is the definition.
'rated new company's' is the wordplay.
'new' indicates anagramming the letters.
'company' becomes 'co' (abbreviation).
'rated' anagrammed gives 'artde'.
'artde'+'co'='ART DECO'
(Other definitions for art deco that I've seen before include "1920s/1930s style" , "Style of 1920s/30s" , "1920-30s design style" , "Geometric style of ornamentation" , "Architecture/design movement of the 1920s and 30s" .)