How many letters does the top answer for “rotating to the left” have?

The most common answer is levorotary (10 letters).

Crossword clue: rotating to the left

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

levorotary 10 letters wn-def

rotating to the left

levorotatory 12 letters wn-def

rotating to the left

of or on the left 50% similar → sinistral