How many letters does the top answer for “a boiling up or over; effervescence. cudworth.” have?

The most common answer is ebullience (10 letters).

Crossword clue: a boiling up or over; effervescence. cudworth.

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

ebullience 10 letters web-def

overflowing with eager enjoyment or approval

ebulliency 10 letters web-def

A boiling up or over; effervescence. Cudworth.

a boiling up; effervescence. boyle. 60% similar → exestuation