Doctor has evil disposition? Nonsense (6)
I believe the answer is:
drivel
'nonsense' is the definition.
(drivel can mean nonsensical speech or writing)
'doctor has evil disposition?' is the wordplay.
'doctor' becomes 'Dr' (abbreviation).
'has' says to put letters next to each other.
'disposition?' is an anagram indicator (I've seen 'disposition' mean this).
'evil' anagrammed gives 'ivel'.
'dr'+'ivel'='DRIVEL'
(Other definitions for drivel that I've seen before include "Gibberish" , "Foolish talk" , "Silly talk, sheer nonsense" , "Worthless talk" , "Balls" .)