On the up and up' is an idiom that means to be honest and above board in one's dealings. The crossword solutions for this term include ABOVEBOARD (10 letters), LEGIT (5 letters), KOSHER (6 letters), ETHICAL (7 letters), LEGAL (5 letters), TRUE (4 letters), LICIT (5 letters), Aslope (6 letters), and RISING (6 letters). All of these words are synonyms for the phrase 'on the up and up' and imply that someone is conducting themselves in a fair and honest manner.