From Longman Dictionary of Contemporary Englishbe wearing your teacher’s/salesman’s etc hatbe wearing your teacher’s/salesman’s etc hat (also have your teacher’s/salesman’s etc hat on) informalWORK/DO WORK to be performing the duties of a teacher etc, which are not your only duties I’m a manager now and only put my salesman’s hat on when one of our sales reps is having real problems. → hat
