How many letters does the top answer for “in a doubtful manner” have?

The most common answer is doubtfully (10 letters).

Crossword clue: in a doubtful manner

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

doubtfully 10 letters wn-def

in a doubtful manner

dubiously 9 letters wn-def

in a doubtful manner

in an ambiguous manner; with doubtful meaning. 50% similar → ambiguously