A female, impartial in business (6)
I believe the answer is:
affair
'business' is the definition.
(thesaurus)
'a female impartial in' is the wordplay.
'female' becomes 'f' (abbreviation).
'impartial' becomes 'fair' ('fair' can be a synonym of 'impartial').
'in' indicates putting letters inside.
'f' put into 'fair' is 'ffair'.
'a'+'ffair'='AFFAIR'
(Other definitions for affair that I've seen before include "Thing to be done with raffia" , "Secret romance" , "Romantic relationship between two unmarried people" , "Business; romance" , "Sexual liaison - concern" .)