Beethoven's fifth opus is a dance! (3)
I believe the answer is:
hop
'dance' is the definition.
(I know that hop is a type of dance)
'beethoven's fifth opus' is the wordplay.
'beethoven's fifth' becomes 'h' (5th letter of 'beethoven').
'opus' becomes 'op'.
'h'+'op'='HOP'
'is a' is the link.
(Other definitions for hop that I've seen before include "Jump; dance" , "A short journey" , "Move on one leg" , "Climbing plant used to flavour beer (3)" , "Leap on one leg" .)