Prevailing mood at second ball (10)

I believe the answer is:

atmosphere

'prevailing mood' is the definition.
(atmosphere can mean a mood or air)

'at second ball' is the wordplay.
'second' becomes 'mo' (both are short periods of time).
'ball' becomes 'sphere' (I've seen this in another clue).
'at'+'mo'+'sphere'='ATMOSPHERE'

(Other definitions for atmosphere that I've seen before include "blue?" , "Air" , "Gas surrounding a planet" , "character" , "Feel" .)

I've seen this clue in The Telegraph and The Times.

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