Tribunal translates to "court" or "tribunal". It's an interesting word choice in this context because it introduces a dramatic and unexpected legal element into what seems like a workplace crush.
The singer expresses a fear of ending up in court due to a potential accusation of sexual harassment, highlighting the serious implications of his feelings for his secretary. This word adds a layer of tension and consequence to the song's narrative.
This song tells a story from a very specific point of view: a boss who is falling in love with his secretary. He watches her go about her day, noticing how she "Puxa as cortinas e abre a janela" (Pulls the curtains and opens the window) with such grace. He sees that she is always smiling and treats his clients well, concluding that for her, "não há sacrifício" (there is no sacrifice). The problem is, his heart can't accept that she's just being a good employee. He thinks her professionalism is a sign of something more, even while his brain tells him it's just "um dever do seu ofício" (a duty of her job).
This is where the song gets really interesting. The boss is completely stuck. He sings directly to her, "Secretária, que trabalha o dia inteiro comigo" (Secretary, who works with me all day), and admits he's in "um grande perigo / De ir parar no tribunal" (great danger / Of ending up in court). He wants to tell her how he feels, but he's terrified his feelings will be mistaken for something much worse. His biggest fear is being "confundido / Por um assédio sexual" (confused / for sexual harassment). It's a surprisingly modern and anxious love song about the complications of a workplace crush.