Ballad penned by each musician (6)
I believe the answer is:
player
'musician' is the definition.
(I know that musician is a type of musician)
'ballad penned by each' is the wordplay.
'ballad' becomes 'lay' (synonyms).
'penned by' is an insertion indicator (inserted letters are penned in).
'each' becomes 'per' ('per' can mean for each).
'lay' inserted within 'per' is 'PLAYER'.
(Other definitions for player that I've seen before include "Actor - musician" , "Batsman perhaps" , "Participant in competitive game" , "Important participant" , "Actor; sportsman" .)