The crossword solution for the term 'YOU CAN'T DO WITHOUT IT' is 'NECESSITY'. NECESSITY is an important concept in philosophy, which states that certain things are required in order to achieve a desired outcome. It is often used to refer to the basic needs of life, such as food, shelter, and clothing. In other contexts, it can refer to the need for certain skills or resources in order to complete a task. In any case, NECESSITY is something that cannot be done without.