Sclero is a colloquial and somewhat intense verb derived from the noun sclerosi, which means 'sclerosis'. However, in modern Italian slang, sclerare (the infinitive form) means to 'freak out', 'lose one's mind', or 'go crazy' due to frustration, anger, or intense emotion.
In the context of the song, the line "E sclero quando non rispondi ai miei messaggi" vividly expresses the singer's intense frustration and emotional turmoil when his messages go unanswered. It's a strong, evocative word that captures a raw, relatable feeling of modern communication anxiety.
Sfera Ebbasta and Elodie spend this one circling the same night over and over. He opens with her asleep on his chest while he smokes, and four lines later he has admitted the ugly part: "Odio chi altro ti ha avuta o fatto sentire al sicuro" (I hate whoever else had you or made you feel safe). That is the whole relationship in a sentence. The hook keeps coming back to "Gocce di pioggia sotto a un cielo nero" (Raindrops under a black sky), and the two of them keep coming back to each other, usually after screaming first.
What makes it land is how blunt the chorus is about the trade. "Quando scopiamo, ti amo per davvero" (When we fuck, I really do love you) is not a romantic line and is not trying to be. The second verse answers with the small, humiliating details of being this invested: driving around the city looking for someone, losing it over unanswered messages, "Tu sai cose di me che non sanno i miei amici" (You know things about me my friends don't know). By the bridge they have stopped pretending anything will change. "Anche questa volta andrà così" (This time too it'll go like this), the storm passes, and they are back out in the street on their own.