The most common and most likely answer to this crossword clue is the 10 letter word PARTICULAR
I've seen this crossword clue in Independent
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More clues leading to the result PARTICULAR
- Specific rail-car put out
- Fussy detail
- Exceptional pressure of the joints
- Railcar put in motion — not at all like The General
- Certain specification
- First section of novel copper initially labelled as rather peculiar
- Fastidious individual
- Special section copper’s taken in by crafty liar
- Noteworthy character crucial to play missing first of cues
- Certain fact
Buddy explains!

The straight part
We know that "Exceptional" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case exceptional = particular.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 PARTICULAR mean?
PARTICULAR noun- A small individual part of something larger; a detail, a point.
- A person's own individual case.
- (chiefly in plural) A particular case; an individual thing as opposed to a whole class. (Opposed to generals, universals.)
- Pertaining only to a part of something; partial.
- Specific; discrete; concrete.
- Specialised; characteristic of a specific person or thing.
- Known only to an individual person or group; confidential.
- Distinguished in some way; special (often in negative constructions).
- Of a person, concerned with, or attentive to, details; minute; precise; fastidious.
- Concerned with, or attentive to, details; minute; circumstantial; precise.
- Containing a part only; limited.
- Holding a particular estate.
- Forming a part of a genus; relatively limited in extension; affirmed or denied of a part of a subject.