Professional

Examples of usage:

1. " On professional business, my dear Martin; strictly on professional business; and I promised my girls long ago that they should accompany me.
   "The World's Greatest Books, Vol III", Arthur Mee and J.A. Hammerton, Eds..
2. This was my last public appearance as a professional actor.
   "The Chronicles of a Gay Gordon", José Maria Gordon.
3. Suppose we leave professional secrets alone, eh?
   "The Man with a Shadow", George Manville Fenn.