The most common and most likely answer to this crossword clue is the 7 letter word ERASERS
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Buddy explains!
The straight part
We know that "Those taking marks off" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case those taking marks off = erasers.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 ERASERS mean?
ERASERS noun- One who erases.
- A thing used to erase or remove something written or drawn by a pen or a pencil.
- A thing used to erase something written by chalk on a chalkboard, by marker on a whiteboard, or by some other erasable implement; a chalkboard eraser, whiteboard eraser, etc.
- An overwriter program used to prevent data recovery.