Police anon cracked one code (10)
I believe the answer is:
napoleonic
'one code' is the definition.
(thesaurus)
'police anon cracked' is the wordplay.
'cracked' is an anagram indicator.
'police'+'anon'='policeanon'
'policeanon' anagrammed gives 'NAPOLEONIC'.
(Other definitions for napoleonic that I've seen before include "The -- Code is a legal system in France" , "Relating to a particular French emperor" , "Old French" , "Relating to Bonaparte" .)