Songs principal first violinist talked of (6)
I believe the answer is:
lieder
'songs' is the definition.
(lied is a kind of song)
'principal first violinist talked of' is the wordplay.
'principal first violinist' becomes 'leader' (I've seen this before).
'talked of' indicates a 'sounds like' (homophone) clue.
'leader' is a homophone of 'LIEDER'.
(Other definitions for lieder that I've seen before include "Relied on German song (6)." , "Art songs for voice and piano" , "Relied on German song genre" , "Musical settings for solo voice and piano" , "German songs for piano and solo voice" .)