How many letters does the top answer for “scientist scientist” have?

The most common answer is bacon (5 letters).

Crossword clue: scientist scientist

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

bacon 5 letters wd-fact-v3

back and sides of a hog salted and dried or smoked; usually sliced thin and fried

yakovlev 8 letters wd-fact-v3

acting scientist 50% similar → basov, berling, chekhova

activism scientist 50% similar → goodall, hanh

aerobatics scientist 50% similar → uhserotermund

aesthetics scientist 50% similar → bolzano, croce, deleuze

agriculture scientist 50% similar → young

agronomy scientist 50% similar → kuo

algebra scientist 50% similar → alkhwarizmi, waerden

anarchism scientist 50% similar → bookchin