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"mutualism" is also used as a crossword clue. If that's what you saw, the answer is often symbiosis (9 letters).
Definitions
A relationship between different species in which both benefit.
Word origin
From mutual + -ism. Compare French mutualisme and Italian, Portuguese, and Spanish mutualismo.
Source: Wiktionary, CC BY-SA 4.0
Used as a crossword answer1 curated clues
01“Two-way benefit”9 letters
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