How many letters does the top answer for “skillfulness by virtue of possessing special knowledge” have?

The most common answer is expertise (9 letters).

Crossword clue: skillfulness by virtue of possessing special knowledge

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

expertise 9 letters wn-def

skillfulness by virtue of possessing special knowledge

expertness 10 letters wn-def

skillfulness by virtue of possessing special knowledge