Baqueá' is a stylized spelling of the Puerto Rican slang word 'baqueada'. It means to be 'backed up' or 'have backup', suggesting someone is well-protected or has powerful connections.
In the song, the line "No brega en la calle, pero está baqueá'" paints a picture of a woman who doesn't involve herself in street life, but is still respected and protected. It's a cool piece of modern slang that adds a layer of toughness and mystery to her character.
This song is all about a secret relationship, a classic theme in reggaeton but done here with so much style. The whole idea is that this woman is one person in public and a completely different one in private. Jhayco, J Balvin, and Bad Bunny all describe her as someone who pretends not to know them when they're out, as the hook says: "Se hace la que no me conoce" (She pretends she doesn't know me). But behind closed doors, it's a different story. She's independent, smart ("en la uni, buenas nota'" [in college, good grades]), and has a 'good girl' image, but at night she calls them because she "le gusta portarse mal" (likes to misbehave).
They get very specific about how intense their secret connection is, calling it "un vicio como la 5-12" (an addiction like the 5-12), which is a reference to the painkiller Percocet. It's a blunt way of saying their time together is powerful and addictive. She has her friends cover for her, keeps her Instagram private, and transforms when she hears a dembow beat. The song paints a picture of a woman who is in complete control of her life and her desires, choosing to keep her wild side a secret from the world, but not from them.