Form of jazz that obviously had to be a hit (5)
I believe the answer is:
bebop
'form of jazz' is the definition.
(I've seen this before)
'be a hit' is the wordplay.
'a hit' becomes 'bop' (I've seen this in another clue).
'be'+'bop'='BEBOP'
'that obviously had to' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for bebop that I've seen before include "Form of modern jazz from about 1940" , "Jazz style of 40s" , "music played in jazz club" , "1940s' form of modern jazz" , "Fast, complex jazz" .)