Crazed fratricide turned on mother (6)
I believe the answer is:
maniac
'crazed' is the definition.
(thesaurus)
'fratricide turned on mother' is the wordplay.
'fratricide' becomes 'cain' (I've seen this in another clue).
'turned' says the letters should be written backwards.
'on' says to put letters next to each other.
'mother' becomes 'ma' (ma can mean mother).
'cain' written backwards gives 'niac'.
'niac' put after 'ma' is 'MANIAC'.
(Other definitions for maniac that I've seen before include "Extremely wild person" , "Insane person" , "fruitcake?" , "Deranged person" , "Crazy person behaving wildly" .)