role (which someone or something plays in a given situation); part; contribution (to a given situation)
彼はその成功に一役買った。
He played a part in its success.
地域活性化に市民が一役を担う。
Citizens play a part in revitalizing the community.
この発明が環境保護に大きな一役を果たした。
This invention played a significant role in environmental protection.