1
general::
Also, against time. In a great hurry, as fast as possible, as in With her term paper due on Monday, she was racing against the clock to finish it, or They were working against time to stay on schedule. The term comes from various sports in which the contestants do not directly compete against each other but instead are timed individually, the winner being the one who is fastest. Its figurative use dates from the mid-1900s.
American Heritage Idioms
2
general::
Phrase(s): against the clock
Fig. in a race with time; in a great hurry to get something done before a particular time. • In a race against the clock, they rushed the accident victim to the hospital.
McGrawhill's American Idioms And Phrasal Verbs