Treated them with a complete addiction treatment (9)
I believe the answer is:
methadone
'addiction treatment' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'treated them with a complete' is the wordplay.
'treated' is an anagram indicator.
'with' means one lot of letters go next to another.
'complete' becomes 'done' (I've seen this in another clue).
'them' is an anagram of 'meth'.
'meth'+'a'+'done'='METHADONE'
Can you help me to learn more?
(Other definitions for methadone that I've seen before include "Synthetic drug taken to replace heroin" , "Drug used in treating heroin addiction" , "Synthetic analgesic" , "Narcotic analgesic drug" .)