Murderous criminal: "I'm a child with nothing to hide" (9)
I believe the answer is:
homicidal
'murderous' is the definition.
(I know that murderous can be written as homicidal)
'criminal i'm a child with nothing to hide' is the wordplay.
'criminal' indicates anagramming the letters.
'with' is a charade indicator (letters next to each other).
'nothing' becomes 'o' (O resembles 0).
'to hide' indicates putting letters inside (some letters hide inside others).
'im'+'a'+'child'='imachild'
'imachild' with letters rearranged gives 'hmicidal'.
'hmicidal' enclosing 'o' is 'HOMICIDAL'.
(Other definitions for homicidal that I've seen before include "likely to kill" , "Lethal" , "out for blood" , "Wanting to kill someone else?" , "Murderous" .)