Bass provides introduction for Everybody Dance (4)
I believe the answer is:
ball
'dance' is the definition.
(ball is a kind of dance)
'bass provides introduction for everybody' is the wordplay.
I cannot really see how this works, but
'bass' could be 'b' (musical abbreviation) and 'b' is located in the answer.
'everybody' could be 'all' (all people) and 'all' is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for ball that I've seen before include "Social function for dancing" , "Sphere - dance" , "Bouncer, say" , "Spherical plaything" , "form of entertainment" .)