You can’t give a clue that’s a homonym of a word on the card. However, if the person outside the game guesses a word that’s a homonym of a word in the card’s name, you do get to claim the prize. For example, if the card is Riku of Two Reflections, you can’t give the word “to” as a clue. However, if the person outside the game guesses “to,” that is a homonym of “Two,” so you claim the prize.