Could she be good for a song? (4)
I believe the answer is:
lady
'song?' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for lady that I've seen before include "mature woman" , "See 2" , "High-class woman" , "Title for a knight's wife" , "Woman, maybe titled" .)