A noted soporific (7)
'soporific' is the definition.
(thesaurus)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for lullaby that I've seen before include "Soothing song for baby - Brahms wrote a good one" , "Song to send one to sleep" , "Soothing song for infants" , "Soporific song" , "Gentle song to put baby to sleep" .)
'a noted soporific' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
This is the entire clue.
Can you help me to learn more?
(Another definition for cradle song that I've seen is " Lullaby".)