The term 'LIGHT UPON' can be broken down into three crossword solutions: SETTLE (6 letters), HIT (3 letters), and STUMBLE (7 letters). SETTLE means to come to rest after a period of movement, HIT means to come into contact with forcefully, and STUMBLE means to walk or move unsteadily. Together, these three words can be interpreted as finding something unexpectedly, such as a solution to a problem or an answer to a question.