Тревогу (trevogu) means "alarm" or "anxiety." It's the accusative form of the noun тревога (trevoga).
In the song, the phrase "Моё сердце бьёт тревогу" (Moyo serdtse b'yot trevogu) literally translates to "My heart beats alarm." This vivid imagery conveys a strong sense of emotional intensity, suggesting the singer's heart is pounding with excitement and perhaps a touch of apprehension due to being deeply in love, as if for the very first time.
This song is a full-on, head-over-heels declaration of love. Islam Itlyashev sings about a feeling so intense, it's like falling in love for the very first time. He says, "Моё сердце бьёт тревогу / Я влюблён как в первый раз" (My heart sounds the alarm / I'm in love like the first time). Everything about this person affects him deeply. Her smile makes his heart race, and in a beautiful poetic line, he says her happiness makes flowers grow: "Распускались в саду розы / От твоих счастливых глаз" (Roses bloomed in the garden / From your happy eyes).
This isn't a quiet, subtle kind of love. The chorus is a repeated, desperate plea to escape with this person to a private world, a place "туда где только ты и только я" (to where it's only you and only me). He insists he simply cannot function without her, repeating over and over, "И не могу прожить и дня / Ты слышишь, без тебя" (And I can't live a day / Do you hear me, without you). It's a simple, direct, and powerful expression of needing someone completely.