The most common and most likely answer to this crossword clue is the 7 letter word ONE-OFF
I've seen this crossword clue in The Times
O
N
E
-
O
F
F
More clues leading to the result ONE-OFF
- Unique type of switch saving energy?
- Special person leaving?
- Unique, if intermittent, about English
- Genuine card found by individual on holiday
- Old and new, very powerfully unique
- Won, we hear, away? It won’t happen again!
- Unique clue for Eno, perhaps
- Reserving energy, switch positions with unique individual
Buddy explains!

The straight part
We know that "Unique" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case unique = one-off.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 ONE-OFF mean?
ONE-OFF noun- Something that is done, created, etc. only once, and often quickly, simply, or improvisationally.
- Something unique and remarkable.
- Occurring once, one-time, independent of any pattern.
- Singular; unique; special; remarkable.