Dance that's authentic, by the sound of it (4)
I believe the answer is:
reel
'dance' is the definition.
(I know that reel is a type of social dancing)
'authentic by the sound of it' is the wordplay.
'authentic' becomes 'real' (authentic means real or genuine).
'by the sound of it' shows a homophone (sound like).
'real' sounds like 'REEL'.
'that's' acts as a link.
(Other definitions for reel that I've seen before include "Lively dance; bobbin" , "Whirl around" , "Totter" , "Lurch; spool" , "Part of a film; stagger" .)