Live band's opening work is jazz (5)
I believe the answer is:
bebop
'jazz' is the definition.
(bebop is a kind of jazz)
'live band's opening work' is the wordplay.
'live' becomes 'be' ('be' can be a synonym of 'live').
'opening' says to take the initial letters.
'work' becomes 'op' (abbreviation for opus).
The first letter of 'bands' is 'b'.
'be'+'b'+'op'='BEBOP'
'is' is the link.
(Other definitions for bebop that I've seen before include "Variety of jazz from the 1940s" , "music played in jazz club" , "Form of modern jazz from about 1940" , "1940s' form of modern jazz" , "Monk composed this" .)