Bona, meliora, ____ : degrees of excellence in things (6)
I believe the answer is:
optima
'things' is the definition.
The answer and definition can be both human attributes as well as being plural nouns.
Perhaps there's an association between them I don't understand?
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for optima that I've seen before include "Ideal conditions" , "Points at which conditions are most favourable" , "Conditions producing the best possible results" .)