Dance begins swinging as McCartney's band appears (5)
I believe the answer is:
samba
'dance' is the definition.
(I've seen this before)
'begins swinging as mccartney's band appears' is the wordplay.
'begins' suggests taking the first letters.
The initial letters of 'swinging as mccartney band appears' is 'SAMBA'.
(Other definitions for samba that I've seen before include "South American dance" , "Lively ballroom dance from Brazil" , "Dance music" , "Dance, originally from Brazil" , "moves from Brazil" .)