Secuestro literally means "kidnapping" or "abduction". It's a very dramatic and intense word that immediately grabs your attention.
In this song, the singer uses it metaphorically in the phrase 'Un secuestro de amor' (A kidnapping of love). He's not talking about a real crime, but rather a fantasy of stealing his love interest away to finally be with them. It's a powerful and memorable way to express his overwhelming desire and frustration.
This song is a hilariously over-the-top declaration of desire. The singer is so desperate for someone that he's decided he has to do something a little crazy, or as he puts it, "algo indebido" (something improper). His solution? A "secuestro de amor" (a kidnapping of love). He's not just fantasizing; he has a whole plan worked out to finally get the person he wants so badly.
His plan is pretty detailed. He sings, "Te amararé las manos... Y te ataré en la cama / De mi departamento" (I will tie your hands... And I will tie you to the bed / In my apartment). To make sure he knows it's really them, he adds, "No apagaré la luz / Para mirar tu cuerpo" (I won't turn off the light / To look at your body). The song even includes a funny spoken part that sounds like a police warning: "Sólo tendrás derecho a permanecer callada" (You will only have the right to remain silent). It's a wild and dramatic way to say 'I can't live without you'.