How many letters does the top answer for “one who writes on heresies.” have?

The most common answer is heresiographer (14 letters).

Crossword clue: one who writes on heresies.

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

heresiographer 14 letters web-def

One who writes on heresies.

one who writes a monograph. 50% similar → monographist

one who writes a treatise. 50% similar → treatiser

one who writes novels 50% similar → novelist