The crossword solution for the term SUFFIX WITH 'RESTRICT' is ION, which is a three-letter word. An ION is an atom or molecule that has gained or lost one or more electrons, giving it a net electric charge. Ions are important in many biological processes, such as muscle contraction and nerve impulse transmission. The suffix 'RESTRICT' is often used to describe something that is limited or restricted in some way. For example, a restriction ION is an ION that is limited in its ability to move through a membrane.