Nothing’s flipping just business (6)
I believe the answer is:
affair
'business' is the definition.
(I've seen this in another clue)
'nothing's flipping just' is the wordplay.
'nothing' becomes 'fa' (slang term - sweet Fanny Adams).
'flipping' says the letters should be written in reverse.
'just' becomes 'fair' (just can mean fair in the sense of showing justice).
'fa' in reverse letter order is 'af'.
'af'+'fair'='AFFAIR'
(Other definitions for affair that I've seen before include "Amorous liaison" , "Concern, matter or illicit romance" , "Extramarital activity" , "Romantic relationship between two unmarried people" , "Illicit liaison" .)