Arrego is a colloquial term in Brazilian Portuguese, often meaning a 'truce' or 'surrender', especially in a difficult situation. It implies giving up or asking for a break from a struggle.
In this song, the artist sings, "Tô pedindo arrego ouvindo o cd do Pablo" (I'm asking for a truce/surrender listening to Pablo's CD). He's metaphorically surrendering to his feelings of heartbreak and seeking solace in music, making it a relatable and emotionally charged word.
This song is about a guy who is really struggling with being single after a breakup. He tries to go out with his friends to have fun, "conhecer umas prima / Tomar umas birita" [meet some girls / have some drinks], but he feels completely out of practice. He says he's "meio enferrujado" [a little rusty] and has forgotten the "ABC da vida de solteiro" [the ABCs of single life] because he was so used to being with his ex. The single life just feels empty to him now.
He's so down that he's given up trying to party and is just listening to sad music, specifically from the Brazilian singers Pablo and Marília Mendonça, who are famous for their heartbreaking songs. He imagines his ex is doing the same thing, singing Marília Mendonça to get over their "trama" [drama]. He admits he's being dramatic, and even though she says she loves him, she's not ready to come back. The song ends with him lost in memories, wishing she were still there and imagining her sending him a text: "Oi preto, tô com saudades, vamo marca de sair sexta?" [Hey babe, I miss you, wanna go out Friday?].