The pale yellow fat of cocoa beans, solid at room temperature and melting near body heat. On chocolate labels, 代可可脂 means a cheaper vegetable fat used instead of it.
可可 is a phonetic loan for 'cocoa'. Watch for related compounds: 可可粉 (cocoa powder), 可可豆 (cocoa bean). The 脂 means 'fat/grease', same character as in 油脂 (fats and oils).