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.
(..) When to scold, when to forgive. When to laugh at her jokes. Except she's the one running me. Ivan. I say this respectfully. One professional to another. You're playing a bad hand. (sighs) I understand you were a ski racer. (..)2015 TvShow: Homeland Title: A False Glimmer Season: 5 Episode 12