Regard as business (7)
I believe the answer is:
concern
I believe this clue is a double definition.
'regard' is the first definition.
(I know that concern is a is a more specific form of the action of regard)
'business' is the second definition.
(eg 'none of your concern', 'none of your business')
'as' acts as a link.
(Other definitions for concern that I've seen before include "Have something to do with" , "Involve" , "Business - anxiety" , "Business organisation" , "Business - worry" .)