Beams put up in an auditorium (4)

I believe the answer is:

rays

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'beams' is the definition.
(rays of light)

I cannot understand how the remainder of the clue works.

(Other definitions for rays that I've seen before include "Beams from sun or moon" , "Single lines of light" , "They swim" , "Flat fish" , "Beams of sunlight" .)

I've seen this clue in The Telegraph.

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