Do nocturnal work on a sonata? (9)
I believe the answer is:
moonlight
'a sonata?' is the definition.
(moonlight sonata by beethoven)
'do nocturnal work on' is the wordplay.
I cannot really see how this works, but
'on' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for moonlight that I've seen before include "Work in a secondary job" , "Work late" , "do an extra job" , "Night-time illumination" , "Ray" .)