Contrasts in light musical number (5,3,3)
I believe the answer is:
night and day
'contrasts' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.
'light musical number' is the wordplay.
I cannot really see how this works, but
'light' could be 'day' (I've seen this in other clues) and 'day' is present in the answer.
'number' could be 'i' (I is an example) and 'i' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
'in' acts as a link.
Can you help me to learn more?
(Other definitions for night and day that I've seen before include "All the time (Sinatra song)" , "Play" , "twenty-four hours in length?" , "24 - 7" , "Cole Porter music" .)