Could you help me to understand the meaning of this idom and wether it is mainly used in written or spoken English?
'To work against the clock'
Thank you
Yes, it's reasonably standard. It means that you have less time to accomplish a task than you think you will need.
It's used in both, but personally, I've heard it spoken more than I've seen it written. But that's usually when I'm watching football, and a team needs to get a goal quickly.