Crossword Genius

B movie opening and closing cinema presentation to create mood (8)

Ross

I believe the answer is:

ambience

'mood' is the definition.
(I know that ambience is a type of mood)

I don't understand how the remainder of the clue works.

(Other definitions for ambience that I've seen before include "Aura (of a place)" , "Surrounding influence" , "Mood of place" , "Surroundings or atmosphere" , "Character and atmosphere of a place" .)

I've seen this clue in The Guardian.
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