No song for a wake? (7)

I believe the answer is:

lullaby

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

'no song' is the definition.
'lullaby' can be an answer for 'song' (lullaby is a kind of song). I am unsure of the 'no' bit.

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for lullaby that I've seen before include "Soporific song" , "Soothing song for infants" , "Song for pacifying baby" , "composition" , "Song to send a child asleep" .)

I've seen this clue in The Sun and The Times.

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