The most common and most likely answer to this crossword clue is the 3 plus 4 letter word BAR CODE
I've seen this crossword clue in The Guardian
B
A
R
C
O
D
E
More clues leading to the result BAR CODE
- Apart from start of couplet, poem is something designed toscan
- Rulebook for lawyers maybe that needs scanning
- Exclude start of Chinese poem that's meant to scan
- Identifying lines when hearing dog recite poetry?
- Unique identifier seen when naked takes doctor aback
- Some Tesco-read bands to decipher?
- Fish in plain lines at the supermarket?
- It stores information about retail costs, primarily in black lines
- Readable arrangement of lines, apart from chapter and verse
- How price is displayed by pub laws
Buddy explains!
The straight part
We know that "Unique identifier" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case unique identifier = bar code.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.