Embuste' is a colloquial term for "lies" or "deception," often implying a trick or a fib. It's a more colorful and less common word than simply saying "mentiras."
In the song, the lyric "Como se deteriora entre tanto embuste'" (How she deteriorates among so many lies) powerfully conveys the emotional toll that repeated deception has taken on the person. It highlights the depth of the betrayal and the impact of being constantly misled.
This song is all about a guy who really messed up a good relationship, and now another guy is stepping in to pick up the pieces! The lyrics tell a story from the perspective of the new guy who's been watching the ex-boyfriend treat his girl badly. He sees her "llora'" [cry] and "sufri'" [suffer] because of the ex's actions, especially for "andar con zorra'" [hanging out with sluts].
The new guy isn't shy about saying, "Fuiste tú el que perdió" [You were the one who lost]. He's been there for her, being her "paño de lágrimas" [shoulder to cry on], and now he's making his move. He's confident that he can treat her better, promising to "poner a entonar como Frank Sinatra" [make her sing like Frank Sinatra] and even saying, "En tu cama me la comía" [In your bed I ate her up] – a pretty blunt way of saying he's moved in! It's a bold and a bit aggressive take on a rebound, with the new guy celebrating his victory over the ex who "nunca valoraste el tiempo que perdió" [never valued the time she lost].