Dramas set to music (6)
I believe the answer is:
operas
'dramas set to music' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for operas that I've seen before include "Musical dramas" , "La Traviata, Aida" , "These shows are a poser, oddly" , "Dramatic musicals in which words are sung" , "Plays in which the words are sung" .)