adore, a door

Adore or adore means to dote on, to be fond of; to love or to worship--
"I just adore a penthouse view..."
"Oh, come, let us adore him..."

A door or a door means one ( a ) door--a panel that opens and closes, used to enter or exit a room, a building, or a vehicle--
I'm going to try the salvage yard, to see if they have a door for my car.
We want to install a door in the side of the garage near the house.

Now that you know that, you can say--
"If you adore the dog, why don't you want a door put in for him?"

Note--"adores" is the third person singular ( he, she, it ) form of "adore", meaning to love or worship--
He adores that dog; he'd never give him up.
Note # 2--"a door's" might describe something that belongs to a door, meaning a panel that opens and closes--
He used a door's  panels to make the shutters.
"A door's" might also be a contraction of "a door is"--
A door's opening--look out!