Outside court, ten mean to reform law (9)
I believe the answer is:
enactment
'law' is the definition.
(thesaurus)
'outside court ten mean to reform' is the wordplay.
'outside' indicates putting letters inside.
'court' becomes 'ct'.
'to reform' is an anagram indicator.
'ten'+'mean'='tenmean'
'tenmean' with letters rearranged gives 'enament'.
'ct' put inside 'enament' is 'ENACTMENT'.
(Other definitions for enactment that I've seen before include "The passing of a bill into law" , "Legal process" , "that needs approval of those in house" , "Portrayal" , "validation" .)