What is a literary Ticking Clock?

In fiction, in real life, and the three clocks of Acid Christmas

As my own novel launches, I find myself thinking about the concept of the “Ticking Clock” in literature. This is a literary device that amps up the tension in stories and also marks time. It’s like an alarm waiting to go off in the characters’ minds and in the reader’s mind. These clocks can be very obvious, like a literal bomb ticking, or an impending …