To exile is not in the legal procedure (6)
I believe the answer is:
outlaw
'to exile' is the definition.
(thesaurus)
'not in the legal procedure' is the wordplay.
'not in' becomes 'out' ('out' is the opposite to 'in').
'the legal procedure' becomes 'law' (I can't justify this - if you can you should give a lot more credence to this answer).
'out'+'law'='OUTLAW'
'is' is the link.
Can you help me to learn more?
(Other definitions for outlaw that I've seen before include "Criminal, bandit" , "Ban; fugitive" , "Ban, prohibit by legislation" , "bar" , "Declare illegal" .)