Child's new sonnet adapted Sondheim number (4,2,3,6)
I believe the answer is:
send in the clowns
'sondheim number' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.
'child's new sonnet adapted' is the wordplay.
'adapted' indicates anagramming the letters.
'childs'+'new'+'sonnet'='childsnewsonnet'
'childsnewsonnet' is an anagram of 'SEND IN THE CLOWNS'.
Can you help me to learn more?
(Another definition for send in the clowns that I've seen is " Sad song".)