The term 'cause of an explosion' can be broken down into three crossword solutions: IRE (3 letters), BOOM (4 letters), and BLAST (5 letters). IRE is a feeling of anger or annoyance, and is often associated with an explosion of emotion. BOOM is a loud, sudden sound, which is often associated with an explosion. BLAST is a strong gust of air or an explosion, which can cause destruction. All three words are related to the cause of an explosion, whether it be emotional, physical, or both.