Authentic-sounding Highland dance? (4)
I believe the answer is:
reel
'highland dance?' is the definition.
(I've seen this before)
'authentic-sounding' is the wordplay.
'authentic' becomes 'real' (I've seen this before).
'sounding' indicates a 'sounds like' (homophone) clue.
'real' is a homophone of 'REEL'.
(Other definitions for reel that I've seen before include "Film spool" , "Scottish/Irish dance" , "Stagger about in lively dance" , "Dance - sway - cotton holder" , "Part of film; dance" .)