Mentally ill - needs new routine before cure starts (8)
I believe the answer is:
neurotic
'mentally ill' is the definition.
(thesaurus)
'new routine before cure starts' is the wordplay.
'new' is an anagram indicator.
'before' says to put letters next to each other.
'starts' says to take the initial letters.
The initial letter of 'cure' is 'c'.
'routine' is an anagram of 'neuroti'.
'neuroti'+'c'='NEUROTIC'
'needs' acts as a link.
(Other definitions for neurotic that I've seen before include "Subject to abnormal anxieties or obsessive behaviour" , "As I recount being subject to abnormal anxieties" , "Emotionally disturbed" , "Very nervy" , "Hypersensitive" .)