The most common and most likely answer to this crossword clue is the 8 letter word SCRUBBER
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More clues leading to the result SCRUBBER
Buddy explains!

The straight part
We know that "one trying hard to clean up" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one trying hard to clean up = scrubber.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 SCRUBBER mean?
SCRUBBER noun- A person or appliance that cleans floors or similar by scrubbing.
- A device that removes impurities from gases.
- A machine for washing leather after the tanpit.
- An animal that breaks away from the herd.
- A prostitute or a slovenly woman.
- (audio, video) A horizontal bar allowing the user to set the playback position.