Code cracked with strange propriety (7)
I believe the answer is:
decorum
'propriety' is the definition.
(I know that decorum is a type of propriety)
'code cracked with strange' is the wordplay.
'cracked' indicates an anagram.
'with' means one lot of letters go next to another.
'strange' becomes 'rum' (synonyms).
'code' is an anagram of 'deco'.
'deco'+'rum'='DECORUM'
(Other definitions for decorum that I've seen before include "good grace" , "modesty" , "Seemly behaviour" , "Decency" , "Propriety of behaviour" .)