Wave from spot in the auditorium (3)
I believe the answer is:
sea
'wave' is the definition.
(thesaurus)
'spot in the auditorium' is the wordplay.
'spot' becomes 'see' (both can mean to notice or observe).
'in the auditorium' shows a homophone (sound like) (ie as heard on a stage).
'see' is a homophone of 'SEA'.
'from' is the link.
(Other definitions for sea that I've seen before include "Cause of flooding" , "North for one" , "Caspian, e.g." , "Large body of salt water" , "Vast expanse" .)