To suggest a doctor may be evil is nonsense! (6)
I believe the answer is:
drivel
'is nonsense' is the definition.
(drivel can mean nonsensical speech or writing)
'to suggest a doctor may be evil' is the wordplay.
I cannot quite see how this works, but
'doctor' could be 'dr' (abbreviation) and 'dr' is found in the answer.
an anagram of 'evil' is 'ivel' which is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for drivel that I've seen before include "Stuff and nonsense" , "Cobblers" , "Slaver" , "Balls" , "Verbal nonsense, rubbish" .)