Cunning code cracked in style (3,4)
I believe the answer is:
art deco
'style' is the definition.
(decorative style)
'cunning code cracked in' is the wordplay.
'cunning' becomes 'art' (both can mean artfulness or trickery).
'cracked' is an anagram indicator.
'in' is an insertion indicator.
'code' with letters rearranged gives 'deco'.
'art' placed inside 'deco' is 'ART DECO'.
(Other definitions for art deco that I've seen before include "1920s/1930s style" , "Nineteen twenty's and thirties style" , "1920s and 1930s style of ornamentation" , "style of interior design" , "modern style" .)