Parts of theatre start to seem completely empty - ninety empty seats! (6)
I believe the answer is:
scenes
'parts of theatre' is the definition.
The definition and answer can be both man-made objects as well as being plural nouns.
Perhaps they are linked in a way I don't understand?
'start to seem completely empty ninety empty seats' is the wordplay.
'start to' says to take the initial letters.
The initial letters of 'seem completely empty ninety empty seats' is 'SCENES'.
Can you help me to learn more?
(Other definitions for scenes that I've seen before include "Divisions of a play" , "Dramatic divisions" , "Landscapes" , "Subdivisions of play acts" , "Subdivisions in theatre" .)