The term DECLARE FIRMLY can be broken down into four crossword solutions: INSIST (6 letters), ASSERT (6 letters), AVER (4 letters), and AVOW (4 letters). All of these words are synonyms for the phrase DECLARE FIRMLY, which means to state something with confidence and conviction. INSIST is to demand something strongly and persistently, while ASSERT is to state something confidently and forcefully. AVER is to state something as a fact or truth, and AVOW is to declare something openly and boldly.