Come back to settle in, but not for good (4)
I believe the answer is:
evil
'good' is the definition.
The answer and definition can be both human attributes as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for evil that I've seen before include "Excellent" , "Extremely wicked" , "Live badly in depravity" , "'The ... that men do lives after them' (Shakespeare)" , "Great wickedness" .)