In which to see plays, or surgery! (7)
I believe the answer is:
theatre
This might be a double definition.
'in which to see plays' is the first definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'surgery' is the second definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
'or' is the link.
Can you help me to learn more?
(Other definitions for theatre that I've seen before include "Building for dramas" , "Building for drama" , "where they're in action?" , "war zone" , "Criterion in London, say" .)