I saw in one thread these explanations:

In the movie Tango & Cash, in the context of a time limit, Gabe says "Clock's running, Ray. Let's go."
Is it idiomatic to just drop the article in speech in this expression?
Thanks.

 

Yes — dropping the article is very common in speech in lots of expressions.

(In BE, 'the clock's ticking' is the usual expression.)

 

Thank you.

 

In AE, it would also be "the clock's ticking", not "running"—although there's a similar expression, "the meter's running". There's also "time's running out".

 

Thank you!