Rear beams in auditorium (5)
I believe the answer is:
raise
'rear' is the definition.
(I know that rear is a more specific form of raise)
'beams in auditorium' is the wordplay.
'beams' becomes 'rays' (rays of light).
'in auditorium' indicates a 'sounds like' (homophone) clue (as the word might sound to an audience).
'rays' is a homophone of 'RAISE'.
(Other definitions for raise that I've seen before include "Put up" , "Contact" , "Increase; elevate" , "Produce" , "Hoist" .)