Original form of jazz (5)
I believe the answer is:
bebop
This might be a double definition.
'original form' is the first definition.
'bebop' can be an answer for 'form' (I have seen 'Form of jazz ' mean 'bebop' so perhaps 'form' could also mean 'bebop'). I'm not certain of the 'original' bit.
'jazz' is the second definition.
(bebop is a kind of jazz)
'of' acts as a link.
Can you help me to learn more?
(Other definitions for bebop that I've seen before include "Jazz genre" , "Jazz style of 40s" , "Jazz-style dance music of the 1940s" , "Form of modern jazz from about 1940" , "Monk composed this" .)