Part of the play, we hear, is not without spectators (4)
I believe the answer is:
seen
'not without spectators' is the definition.
I can't judge whether this defines the answer.
'part of the play we hear' is the wordplay.
'part of the play' becomes 'scene' ('scene' is part of 'play').
'we hear' indicates a 'sounds like' (homophone) clue.
'scene' is a homophone of 'SEEN'.
'is' is the link.
Can you help me to learn more?
(Other definitions for seen that I've seen before include "watched" , "Witnessed" , "Perceived by sight" , "Viewed" , "Noticed" .)