The term 'call into question' can be expressed in a variety of ways, as evidenced by the crossword solutions given. OPPUGN (6 letters) means to attack verbally or DISPUTE, IMPEACH (7 letters) means to CHALLENGE the credibility of someone, QUERY (5 letters) means to ask questions, DISPUTE (7 letters) means to argue or disagree, CHALLENGE (9 letters) means to question the validity of something, DOUBT (5 letters) means to have reservations about something, ieach (5 letters) means to call into question, and CONTEST (7 letters) means to oppose or DISPUTE. All of these words are related to the idea of questioning or challenging something, which is the essence of the phrase 'call into question'.