Did Beethoven write one by moonlight? (6)
I believe the answer is:
sonata
'moonlight?' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for sonata that I've seen before include "Musical composition with three or more contrasting movements" , "composition for piano, perhaps" , "Piece of classical music" , "Music for a soloist" , "Chamber work" .)