Songs, 3's boss said (6)
I believe the answer is:
lieder
'songs' is the definition.
(lied is a kind of song)
'boss said' is the wordplay.
'boss' becomes 'leader' (I've seen this before).
'said' shows a homophone (sound like).
'leader' is a homophone of 'LIEDER'.
'3's' acts as a link.
This may not be correct. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for lieder that I've seen before include "songs from Berlin?" , "songs by Schumann?" , "German songs of the Romantic period" , "Art songs for voice and piano" , "numbers in German" .)