How many letters does the top answer for “the trait of believing in the honesty and reliability of others” have?

The most common answer is trustfulness (12 letters).

Crossword clue: the trait of believing in the honesty and reliability of others

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

trustfulness 12 letters wn-def

the trait of believing in the honesty and reliability of others

trustingness 12 letters wn-def

the trait of believing in the honesty and reliability of others