Song about scoundrel's pastoral paradise (7)
I believe the answer is:
arcadia
'pastoral paradise' is the definition.
(I've seen this in another clue)
'song about scoundrel's' is the wordplay.
'song' becomes 'aria' (piece of music in an opera).
'about' is an insertion indicator.
'scoundrel' becomes 'cad' (cad is a kind of scoundrel).
'aria' placed around 'cad' is 'ARCADIA'.
(Other definitions for arcadia that I've seen before include "such as Strephon enjoyed?" , "rural idyll" , "Idealised pastoral setting - Greek region" , "modern play" , "Idealised rustic paradise" .)