Business expense that's up in the air? (8)
I believe the answer is:
overhead
I believe this clue is a triple definition!
'business expense' is the first definition.
(ongoing cost of operating a business)
'that's up' is the second definition.
(thesaurus)
'in the air?' is the third definition.
(thesaurus)
(Other definitions for overhead that I've seen before include "General business expense" , "Expenses" , "In the sky - type of door or projector" , "Cost of upkeep of business premises, etc" , "A running cost of a business" .)