The most common and most likely answer to this crossword clue is the 6 letter word FORMAL
I've seen this crossword clue in Financial Times
F
O
R
M
A
L
More clues leading to the result FORMAL
- Official document to be completed by a learner driver
- Starchy class at Lancing originally
- Precise as regards unfinished shopping centre
- Official document the French sent up
- Like court dress, perhaps, appropriate to a man? Not entirely
- Serious little creature swallowing soldier at sea
- Essential FM introduces halves of eg German exam
- Stiff examination encapsulating misery primarily, fellow gets over it
- Short man’s stiff
- Official room to feed horse
Buddy explains!

The straight part
We know that "Official" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case official = formal.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 FORMAL mean?
FORMAL noun- Formalin.
- An evening gown.
- An event with a formal dress code.
- A formal parameter.
- Being in accord with established forms.
- Official.
- Relating to the form or structure of something.
- Relating to formation.
- Ceremonial or traditional.
- Proper, according to strict etiquette; not casual.
- Organized; well-structured and planned.
- Relating to mere manipulation and construction of strings of symbols, without regard to their meaning.