Song largely composed next to city lake (8)
I believe the answer is:
madrigal
'song' is the definition.
(madrigal is a kind of song)
'largely composed next to city lake' is the wordplay.
'largely' means to remove the last letter (most but not all of the letters).
'composed' becomes 'made'.
'next to' means one lot of letters go next to another.
'city' becomes 'riga' (Riga is an example).
'lake' becomes 'L' (geographical abbreviation).
'made' with its final letter removed is 'mad'.
'mad'+'riga'+'l'='MADRIGAL'
(Other definitions for madrigal that I've seen before include "Part-song" , "Unaccompanied harmonised part song" , "Elaborate part song" , "Part song for unaccompanied voices" , "air" .)