Here are some idiomatic expressions built around words beginning with letter D.
Damn someone with faint praise
To damn someone with faint praise is to praise them in such a way that it appears you are actually criticizing them.
Put a damper on
To put a damper on something is to make it less enjoyable.
In the dark
When you are in the dark, you are in a state of ignorance.
A shot in the dark
A shot in the dark is a wild guess.
Dash something off
To dash a letter off is to write it hurriedly.
Call it a day
To call it a day is to decide to stop doing an activity.
Day in and day out
When something happens day in and day out, it happens continuously or repeatedly over a long period of time.
Scare the daylights out of someone
To scare the daylights out of someone is to do something that scares them severely.
The dead of night
The dead of night is the darkest and quietest part of the night.
The dead of winter
The dead of winter is the coldest part of winter.
Fall on deaf ears
When something falls on deaf ears, it is ignored.
Turn a deaf ear
To turn a deaf ear is to refuse to listen or respond.
Deal someone a blow
To deal someone a blow is to hit them.