Final answer:
The sentence provides a synonym as a context clue by giving a definition or equivalent term adjacent to the unknown word 'animosity', directly explaining it means 'hatred'.
Step-by-step explanation:
The type of context clue given in the sentence 'His animosity, or hatred, of his sister divided the family.' is a synonym. This is because the sentence provides a definition or a synonymous term adjacent to the unknown word, thereby helping the reader understand the meaning of 'animosity' by stating it is the same as 'hatred'. The use of a synonym as a context clue is immediate and direct, as it offers an equivalent word right there in the sentence, making it easier for the reader to comprehend.