white lie
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A lie that is told in order to be polite or to stop someone from being upset by the truth

which way the wind blows
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If a person tries to discover which way the wind blows/is blowing, he/she tries to discover information about a situation, especially other people's opinions, before he/she takes action.
John knows which way the wind blows and always acts accordingly.

take one's breath away
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To make someone feel surprised and excited.
The beautiful new cinema took my breath away.

a slip of the tongue
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If you describe something you said as a slip of the tongue, you mean that you said it by mistake.

to be born in purple
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It was originally used to refer to babies born to the members of the royal family.

lose one's temper
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Lose self-control.

bottom line
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Main result/factor.
The bottom line is, I don't have enough money.

castles in the air
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Plans that have very little chance of happening.

apple of one’s eye
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Special favorite, beloved person or thing.
The youngest was the apple of his father's eye.

bring home the bacon.
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To bring home the bacon means to earn the household income.

a drop in the bucket.
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A very small amount compared to the amount needed

at first sight.
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Used to describe your first impression of someone or something, usually to indicate that this first impression was wrong or incomplete.
Love at first sight

roughly speaking
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Not being totally accurate (used as a phrase to specify).

put food on the table
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To provide enough money to cover basic necessities.

put your heart and soul into something
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If you put your heart and soul into something, you do it with a great deal of enthusiasm and energy.

nail something down
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To finalize

man of his word
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A person who can be trusted to keep a promise; a reliable person.

odds and ends
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Various things of different types, usually small and not important, or of little value.

on hand
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If someone or something is on hand, they are near and able to be used if they are needed.
Do you have a calculator on hand?

which way the wind blows
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What the real situation is.

The real meat of things
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The most important part or the main part of something.

under cover of something
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Hidden or protected by something.
He was working undercover at that time.

super-duper
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Extremely good.

keep in mind
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To be careful to remember something important.

bear in mind
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If you tell someone to bear something in mind or to keep something in mind, you are reminding or warning them about something important which they should remember.

the chicken and egg problem
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If you describe a situation as a chicken and egg situation, you mean that it is impossible to decide which of two things caused the other one.