Complex sentence: They are resentful of Rosy Ryan (Sarah Miles), the spoilt daughter of the local publican Tom Ryan (Leo McKern), who himself is an informer for the British hoping to keep the peace in the village.
Split into simpler sentences: They are resentful of Rosy Ryan (Sarah Miles), the spoilt daughter of the local publican Tom Ryan (Leo McKern). In fact, however, he is a secret informer for the British, hoping to keep the peace in the village.