Am in a confused state - it's a mental illness (5)
I believe the answer is:
mania
'it's a mental illness' is the definition.
(thesaurus)
'am in a confused' is the wordplay.
'am' becomes 'MA' (synonyms).
'confused' is an anagram indicator.
'in'+'a'='ina'
'ina' is an anagram of 'nia'.
'ma'+'nia'='MANIA'
'state' acts as a link.
This may not be right. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for mania that I've seen before include "Aberration" , "Insanity" , "Obsessive enthusiasm" , "Mental disorder that results in excessive or violent responses" , "Passion -- mood disorder" .)