Is this calculator written in Python clean/good?
This code is broken into multiple unnecessary functions. Below is all thats needed:

operations = {
    "+": lambda x, y: x + y,
    "-": lambda x, y: x - y,
    "*": lambda x, y: x * y,
    "/": lambda x, y: x / y
}

def calculate():

    # Get numbers #
    one, two = input("Enter two numbers separated by a space: ").split()

    while operator := input("Enter an operator: + - * /"):
        if operator in ["+", "-", "*", "/"]:
            print(operations[operator](int(one), int(two)))
            return


Getting multiple values from input

Instead of prompting for each number, simply ask for two numbers separated by a space then split the input with a given delimiter, by default a space. .split returns a list, and since you only anticipate two values, can assign the output to one, two.

Walrus Operator

If you're using python-3.8, you can utilize the walrus operator, also called assignment expressions. It allows you to assign and return a value in an expression. This reduces the need to define a variable before the loop and use it.

Checking in

I do believe using a list/tuple instead of a string when checking in this particular case because it can catch some invalid input. A catch such as if operator in "+-*/":, it will allow "+-" as a valid operator, which we don't want. So good job there.

Lambdas

I've decided to use lambdas here because it's much easier to store them in a dictionary and then simply retrieve the value from the dictionary with the operator. If you want to learn more about how lambdas work, this Google Search brings up a plethora of sources that can explain the concept much better than I can.