The term 'Tango Requirement' refers to the need for TWO people to dance the tango. The TWO people must be in a PAIR, with each person taking on a specific role. This is because the tango is a partnered dance that requires TWO people to move in unison and in harmony with each other. The TWO people must also have TWO distinct roles, with one leading and the other following. This is why the crossword solutions for the term 'Tango Requirement' are 'PAIR' (4 letters) and 'TWO' (3 letters).