To "tidy" something is to make it clean and neat. This word is often used with the word "up."
We have to tidy up the house before our guests arrive.
Asha wanted to tidy herself up before her job interview, so she went to the ladies’ restroom to put on some make up.
You should tidy yourself up before a picture is taken. You want to look your best, don’t you?
They keep their house very tidy. (This sentence uses "tidy" as an adjective.)
This is a very tidy neighborhood.
He needs to tidy up.
Sometimes this word is used to describe an amount of money, usually a large amount:
Bob made a tidy profit on the sale of his house.
A college degree in computer programming often results in a tidy income upon graduation.
We made a tidy sum of money last year.
*One of my students asked me this morning about the word "spruce." It can be used in place of the word "tidy" when preparing oneself or cleaning up: She wants to spruce up a little before her guests arrive.)