The most common and most likely answer to this crossword clue is the 8 letter word TAXPAYER
I've seen this crossword clue in The Times
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More clues leading to the result TAXPAYER
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The straight part
We know that "Rates contributor" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case rates contributor = taxpayer.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does TAXPAYER mean?
TAXPAYER noun- A person who is subject to, liable for, or pays tax as opposed to a nontaxpayer who is neither the subject nor the object of revenue laws.
- All of the people, collectively, in a population who pay tax (especially used in the context of the government financing something using the tax revenue).