We hear No 1 songs (6)
I believe the answer is:
lieder
'songs' is the definition.
(lied is a kind of song)
'we hear no 1' is the wordplay.
'we hear' indicates a 'sounds like' (homophone) clue.
'no 1' becomes 'leader'.
'leader' sounds like 'LIEDER'.
(Other definitions for lieder that I've seen before include "Musical settings for solo voice and piano" , "Relied on classical German song" , "songs from Berlin?" , "Relied on German song (6)." , "Art songs for voice and piano" .)