If the result of something is a close call, it is almost impossible to distinguish between the parties involved and to say who has won or whatever. It can also mean that you very nearly have a serious accident or get into trouble.
If members of an organisation close ranks, they show support for each other publicly, especially when being criticised. It is a military term- when soldiers close ranks, they stand closer together so that it is difficult to pass through them.
If people try to fix something after the problem has occurred, they are trying to close the stable door after the horse has bolted.
'Close the barn door after the horse has bolted' is alternative, often used in American English.
If an activity is referred to as a clutch play, it means that the activity was the key to the success or failure of the venture. For instance, a clutch play in a baseball game may be striking out a batter with the bases loaded.