How many letters does the top answer for “not openly made known” have?

The most common answer is secret (6 letters).

Crossword clue: not openly made known

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

secret 6 letters wn-def

something that should remain hidden from others (especially information that is not to be passed on)

unavowed 8 letters wn-def

not openly made known

made known or openly avowed 60% similar → declared