A good likeness (4)
I believe the answer is:
icon
This clue might be a double definition.
'a good' is the first definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'likeness' is the second definition.
(I've seen this in another clue)
Can you help me to learn more?
(Other definitions for icon that I've seen before include "Computer-screen symbol" , "Representation on wooden panel of saint" , "Religious painting of Greek origin" , "Symbolic person or image" , "Saint's image" .)