Perform other work: here's one sonata (9)

I believe the answer is:

moonlight

I'm a little stuck... Click here to teach me more about this clue!

'one sonata' is the definition.
(moonlight sonata by beethoven)

I cannot understand how the rest of the clue works.

(Other definitions for moonlight that I've seen before include "Reflected illumination" , "Natural (and romantic?) illumination" , "Beethoven sonata" , "Beethoven composition for piano" , "Work late" .)

I've seen this clue in The Independent.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.