Weeping, into a mental disorder (11)
I believe the answer is:
lamentation
'weeping' is the definition.
(thesaurus)
'into a mental disorder' is the wordplay.
'disorder' is an anagram indicator (I've seen 'diseased' mean this (I've seen this in other clues)).
'into'+'a'+'mental'='intoamental'
'intoamental' anagrammed gives 'LAMENTATION'.
(Other definitions for lamentation that I've seen before include "sad expression" , "Regret" , "Keen" , "Show of grief" , "Expression of sorrow" .)