There are certain uncountable nouns used in idiomatic phrases that behave in this way. After all, we see similar wording with:
- swim in the ocean
- a stab in the dark
- bring home the bacon
- another one bites the dust
- turn up the volume
- hands in the air
However, I understand your confusion! After all, we generally say:
- a moment in time (not a moment in the time)
- in sickness and in health (not in the health)
- bundle of joy (not bundle of the joy)
- best of luck (not best of the luck)
- taken with a grain of salt (not with a grain of the salt)
I can't think of a foolproof rule that would tell you when to include a definite article, and when to omit one. You're right to say that some of it is simply idiomatic – or at least seems to be. But do remember that you don't need to be talking about "some specific X" to use a definite article; that's only one use of a few. Oddly enough, when I say, "My daughter played the clarinet," we aren't talking about a specific clarinet; however, when we say, "My son ate the hamburger," we are likely talking about a specific hamburger (like the one you left on the counter, for example.) Here's another interesting one: if I say "Turn up the radio," then I'm referring to a specific radio; however, if I say, "This song got a lot of play on the radio," I'm not talking about a specific radio, but radio playlists in general.
