Why does Iros want to expel Odysseus from the palace?
In Odyssey 18, we find Odysseus disguised as a beggar inside his own home on Ithaca. His mission is to destroy the 108 suitors who have been harassing his wife Penelope for the past several years. In Book 18, Odysseus wants to test the hospitality of the various suitors, so he goes around and begs from them to see if he will receive hospitable treatment.
Unfortunately for Odysseus, another beggar named Irus (also spelled Iros) has essentially claimed Odysseus' palace as his "turf" and so Irus does not appreciate the competition from Odysseus. Given this, Irus acts in a hostile way toward Odysseus and challenges Odysseus to a fight, a battle which Odysseus wins. Odysseus then drags Irus out of the palace.
This event foreshadows Odysseus' destruction of the suitors and results in an ironic blessing from the suitors, who offers Odysseus congratulations for his victory over Irus:
"Stranger, may Zeus and the other gods grant you your heart’s dearest wish, your fondest desire, since you’ve ended that greedy fellow’s begging here." (A.S. Kline translation)