。
He adapted to the circumstances as they came.
Literal
He [topic-は] to-the-situation adaptation [of-の] measure [object-を] took.
臨機応変 ('adapting to circumstances') is a 四字熟語 (four-character idiom) — literally 'facing-circumstances, responding-to-change.' ~の処置をとる ('take measures of X') frames it as an action. A formal, idiomatic way to say someone 'rolled with it.'