Can't figure out how to remove items from a list by index.

So I am trying to complete this challenge.

I am hoping to create a list from the word then loop through each letter while comparing to the not allowed vowels. Next I want to remove the letters that don't follow the rule then .join the list back into a single script word. I am able to join the list back up and identify the error characters, however a problem arises when I try to remove items from the list. I keep getting a value error. Should I be raising an error and removing later instead of attempting to delete it right in the if statement?

I know I can find the solution if I tried but I do want to figure it out on my own. Any guidance would be greatly appreciated!

PS: I know my function doesn't have the right name, I am working on it in workshop to diagnose my issues easier then I pasted it over.

na_letter_low = ['a','e','i','o','u']
na_letter_up = ['A', 'E', 'I', 'O', 'U']
def d_vowel(word):
    split_word = list(word)     #duplicating word variable to not edit original
    for letter in split_word:   #creating loop to run through and test each letter in the word
        index = 0               #Creating an index variable to scan through not allowed vowels
        while index < 6:        #looping through all vowels on first letter in word
            if letter == na_letter_low[index] or na_letter_up[index]:
                split_word.pop(index)
            else:
                index += 1            
    return "".join(split_word)
print(d_vowel("HelloWorld"))