Valuable violin not primarily needed for jazz (4)
I believe the answer is:
trad
'for jazz' is the definition.
(trad jazz is a type of jazz)
'valuable violin not primarily' is the wordplay.
'valuable violin' becomes 'strad' (I've seen this in another clue).
'not primarily' means to remove the first letter.
'strad' with its first letter taken off is 'TRAD'.
'needed' acts as a link.
(Other definitions for trad that I've seen before include "Style of jazz" , "(Of jazz) traditional" , "Conventional (jazz)" , "Type of jazz or folk" , "Form of folk or jazz" .)