They consist of scenes (4)
I believe the answer is:
acts
'they consist of scenes' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for acts that I've seen before include "Cast in major divisions of plays, like Shakespeare's" , "Major divisions of play" , "Book; play parts" , "Parliaments pass them" , "Laws passed" .)