How many letters does the top answer for “having a nucleus or occurring in the nucleus” have?

The most common answer is nucleate (8 letters).

Crossword clue: having a nucleus or occurring in the nucleus

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

nucleate 8 letters wn-def

form into a nucleus

nucleated 9 letters wn-def

having a nucleus or occurring in the nucleus

having a nucleus; nucleated. 50% similar → nucleate