He deals with the customers in a very 'professional' way. = He is very 'professional' in dealing with the customers.
a golf/tennis 'professional' [=a skillful golf/tennis player whose job is to teach other people how to play]
I was impressed by the calm and 'professional' way she handled the crisis.
(..) of my life. Up until then, at least. So what happened next ? You mean... did we do it ? Sorry to disappoint you, Mr Bodine. Jack was very professional. Thank you. What are you doing ? Will you put this back in the safe for me ? Would you excuse me ? (..)1997 Titanic