Clint's maybe got a little extra luck in him that attunes him to danger, a little voice on the wind that whispers inaudibly when there’s something he should look twice at to make sure he sees it. But mostly, Clint’s just the product of a fucked up bloodline doing his best to survive.
What he's noticing right now is that every inch of the brooding man before him screams danger. Clint is not sure if it's inherent to the guy himself; some entities feel like danger if they're the right combination of powerful and pissed off. But he suspects that it's the foreboding sense that whatever this man has to ask from him, it's not going to end well. Whether that’s for him or the other guy, Clint can't be sure.