be watching the clock idiom (also have/keep your eye on the clock)
（通常因厌烦或急于离开而）老是看表
to be looking to see what the time is, usually because you are bored or eager to leave
I had a train to catch, so I was watching the clock all through the meeting. 我得赶火车，所以开会的时候我一直在不停地看时间。