State mostly judicious reason against wrongdoing (9)
I believe the answer is:
wisconsin
'state' is the definition.
(I know that Wisconsin is a state)
'mostly judicious reason against wrongdoing' is the wordplay.
'mostly' means to remove the last letter (most but not all of the word).
'judicious' becomes 'wise' (I've seen this before).
'reason against' becomes 'con' (I've seen this in another clue).
'wrongdoing' becomes 'sin' (sin is a kind of wrongdoing).
'wise' with its last letter taken away is 'wis'.
'wis'+'con'+'sin'='WISCONSIN'
(Other definitions for wisconsin that I've seen before include "US state, capital Madision" , "US state, capital Madison" , "Northern state" , "American state, capital Madison" , "US state bordering Lakes Superior and Michigan" .)