Embaixador translates to "ambassador". It's an interesting and somewhat unexpected word to find in a romantic country song, making it stand out.
In this context, Gusttavo Lima, who is famously known as "O Embaixador" (The Ambassador) in Brazilian music, uses it as a self-referential nickname. While it literally means a diplomatic representative, here it signifies his status and perhaps his role in spreading love through his music, adding a unique touch to the lyrics.
"Sempre Seu Homem" ("Always Your Man") is Gusttavo Lima's promise song, about the moment falling in love stopped feeling like a risk and started feeling like home.
He walks through how it happened: the first time together, feeling caught in her spell ("preso no seu laço"), and finally letting his guard down enough to hand over his heart. There's no drama here, just plain relief that the love turned out to be worth it.
The title line repeats like a vow: he made her his woman so he could always be her man. It's less a grand declaration and more a quiet, steady commitment, the kind sertanejo does especially well.