The most common and most likely answer to this crossword clue is the 6 letter word AXEMAN
I've seen this crossword clue in The Guardian
A
X
E
M
A
N
More clues leading to the result AXEMAN
- Guitarist celebrity Times article recalled
- Chopper with a cross on rotating handle
- Guitarist, celebrity, coming over after a kiss
- Executioner initially appalled by up-and-coming celeb
- Cut staff for someone on 8 21?
- One making cuts, resetting an exam
- A vote celebrity reversed for one making cuts
- Slash, perhaps, as one cutting costs
- He’s cutting guitarist
- A cross celebrity stands up guitar player
Buddy explains!

The straight part
We know that "someone on 8 21" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case someone on 8 21 = axeman.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 AXEMAN mean?
AXEMAN noun- A man who wields an axe.
- A musician who plays a guitar or saxophone.