How many letters does the top answer for “a linguist who specializes in the study of grammar and syntax” have?

The most common answer is grammarian (10 letters).

Crossword clue: a linguist who specializes in the study of grammar and syntax

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

grammarian 10 letters wn-def

a linguist who specializes in the study of grammar and syntax

syntactician 12 letters wn-def

a linguist who specializes in the study of grammar and syntax