。
She did a lot of volunteer work for the Red Cross.
Literal
She [topic-は] Red-Cross [for-のために] voluntary labor [object-を] much did.
赤十字 (せきじゅうじ) is the Red Cross — literally 'red cross.' のために marks the beneficiary of the work: 'for the Red Cross.' 自発的 (じはつてき) means 'voluntary' or 'spontaneous,' and 労働 (ろうどう) means 'labor.' The phrase 自発的な労働 is somewhat formal and stiff — in everyday Japanese, ボランティア (volunteer) would be more natural.