The most common and most likely answer to this crossword clue is the 8 letter word STAINING
I've seen this crossword clue in The Daily Telegraph
S
T
A
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N
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Buddy explains!

The straight part
We know that "Making mark" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case making mark = staining.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 STAINING mean?
STAINING verb- To discolour.
- To taint or tarnish someone's character or reputation
- To coat a surface with a stain
- To become stained; to take a stain.
- To treat (a microscopic specimen) with a dye, especially one that dyes specific features
- To cause to seem inferior or soiled by comparison.