Baltic capital left behind crazy song (8)
I believe the answer is:
madrigal
'song' is the definition.
(madrigal is a kind of song)
'baltic capital left behind crazy' is the wordplay.
'baltic capital' becomes 'riga' (I've seen this before).
'left' becomes 'l' (common abbreviation).
'behind' means one lot of letters go next to another.
'crazy' becomes 'mad' ('mad' can be a synonym of 'crazy').
'riga'+'l'='rigal'
'rigal' put after 'mad' is 'MADRIGAL'.
(Other definitions for madrigal that I've seen before include "glee" , "Drag Liam around to hear an unaccompanied song" , "air" , "Elizabethan song" , "Unaccompanied harmonised part song" .)