The question is incomplete. Its full version is:
What is an important context clue in determining an appropriate definition for a particular word?
A. the part of speech
B. the writer's use of figurative language
C. the word's antonyms
D. the etymology
The answer is A (the part of speech).
The part of speech in which the word appears is what gives us the clue for determining the most accurate definition of a particular word.
Instead, figurative language has implicit meaning, antonyms give the opposite meaning (but the meaning may change according to the context), and etymology studies the origins of words, hence, these options are not accurate.