Song about rogue in rural idyll (7)
I believe the answer is:
arcadia
'rural idyll' is the definition.
(I've seen this before)
'song about rogue' is the wordplay.
'song' becomes 'aria' (piece of music in an opera).
'about' means one lot of letters goes inside another.
'rogue' becomes 'cad' (I've seen this in another clue).
'aria' enclosing 'cad' is 'ARCADIA'.
'in' acts as a link.
(Other definitions for arcadia that I've seen before include "In Greece, its capital is Tripoli" , "Tom Stoppard play" , "rural area" , "Idealised Greek district" , "modern play" .)