Cloak-and-dagger

A cloak-and-dagger activity involves secrecy and plotting.   

“Politicians are accustomed to cloak-and-dagger diplomacy and negotiations.”

Climb on the bandwagon

To climb on a bandwagon is to do something because it is popular and everyone else is doing it.  

“I don’t particularly like bungee jumping but that’s what all my friends are doing.  Maybe I’ll climb on the bandwagon just to please them.”

Clear as bell

If something is as clear as a bell, it is very clear or easy to understand.   

”I wonder why he misunderstood the instructions. It was clear as a bell.”

Clean hands

Someone who has clean hands is free from fault or any wrongdoing.   

“He who accuses someone of an offense must come with clean hands.”

Chow

This is another name for food.  

“How’s the chow at the school canteen?”

Chink in someone's armour

This refers to a weakness that can be taken advantage of.  

“Only people close to him could see the chink in his armour.”