RIGHT THING TO DO›something you must do because it is morally or legally right: a moral duty[+ to do sth]Rail companies have a duty to provide safe transport.
JOB›something you do as part of your job or because of your position: professional/official duties
on/off duty›If a doctor, police officer, etc is on duty, they are working, and if they are off duty, they are not working: I'm on duty tomorrow night.