"We must listen."
Translation:Tá orainn éisteacht.
Tá is a verb.
There are a range of phrases formed with tá and a prepositional phrase. When the phrase involves a noun, the prepositional pronoun usually comes after the noun (tá úll agam, tá úll uait), when the phrase involves a verb, the prepositional pronoun usually comes before the verb, so that you don't have two verbs coming together (Tá uirthi rith, Tá faoi siúl go Baile Átha Cliath).