The most common and most likely answer to this crossword clue is the 4 letter word SANS
S
A
N
S
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The straight part
We know that "Bar" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bar = sans.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 SANS mean?
SANS adjective- Short for sans serif.
- Without; lacking
- A letter of the Archaic Greek alphabet (uppercase Ϻ, lowercase ϻ) that came after pi and before qoppa.
- A sanatorium.