against the clock

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.

The adverb has one meaning:

Meaning #1: as fast as possible; before a deadline
  Synonym: against time