The most common and most likely answer to this crossword clue is the 6 letter word PASSER
I've seen this crossword clue in The Daily Telegraph
P
A
S
S
E
R
More clues leading to the result PASSER
- Old-fashioned Republican next to witness
- Spy sabre, exotic, for witness?
- Times following up proposition Queen is not a good Samaritan?
- Meet the cost of accommodating second Balkan potential witness
- As casual observer, spy bears cavorting
- Wages securing South Balkan resident’s walk-on role?
- Quarterback tossed spears
Buddy explains!
The straight part
We know that "potential witness" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case potential witness = passer.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 PASSER mean?
PASSER noun- One who succeeds in passing a test, etc.
- Someone who passes, someone who makes a pass.
- A passed pawn.
- One who passes; a passer-by.
- One who is able to "pass", or be accepted as a member of a race, sex or other group to which society would not otherwise regard them as belonging.