The crossword solution for the term NOT JUST IF is 'WHEN', which is a four-letter word. The word 'WHEN' is used to refer to a specific point in time, such as a particular moment, day, or year. It can also be used to indicate the circumstances under which something happens, such as 'WHEN I'm feeling down'. In this context, the phrase 'not just if' implies that something will happen regardless of the circumstances.