Answer the call of nature

Teddy was on a walk in the forest when suddenly -- and without warning -- he had to answer the call of nature. "I really must obey the call of nature." he whispered. Fortunately for Teddy, there was a WC nearby for to answer/obey the call of nature is to go to the bathroom.

Brush up on

Professor Oxbridge has been invited to give a talk on the history of his school. He hasn't read anything about it for so long that he'll have to brush up on it. That is, he'll have to refresh his knowledge of it. "There, I've brushed up on the subject." Professor exbridge smiled.

To be on the safe side

Those who take extra precautions to reduce or eliminate the possibility of a mistake, an error or even danger are taking measures to be on the safe side. "To be on the safe side Felix always makes certain his valuables are kept in a secure place."

Daylight robbery

One day Malcolm went shopping. He was so shocked at the cost of things that he got angry. "These prices are absurd !" he shouted. "It's daylight robbery to change such prices !" What Malcolm was saying was that in his opinion, the prices were so high that shopkeepers seemed to be robbing people of their money.

Deliver the goods

The goods referred to in this idiom mean an expected -- or hoped for -- result. "Deliver" means to come forth with. "Now that I've had my car repaired it's running fine and delivering the goods." ( Hoped-for results ) "I knew Sam would deliver the goods once he understood his job. That's why I promoted him." the boss said. ( Expected results )