Relate to business (7)
I believe the answer is:
concern
This clue is a double definition.
'relate to' is the first definition.
(thesaurus)
'business' is the second definition.
(eg 'none of your concern', 'none of your business')
(Other definitions for concern that I've seen before include "Feeling of anxiety or sympathy" , "Firm - interest" , "Involve" , "Affect; solicitude" , "Business - anxiety" .)