The crossword solution for the term THEY'RE NOT FREE OF CHARGE is 'IONS', which stands for 'Ions' or 'Ionized Particles'. Ions are atoms or molecules that have gained or lost an electrical charge due to the transfer of electrons. They are important in many biological processes, such as muscle contraction and nerve impulse transmission. Ions also play a role in the formation of chemical bonds and the regulation of pH levels in the body.