She played an active role in the women's liberation movement.

Literal

She [topic-は] women's-liberation-movement [in-で] active role [object-を] did.

婦人解放運動 (ふじんかいほううんどう, 'women's liberation movement') is a formal compound. 積極的な役割をした means 'played an active role.' で marks the field of activity.