The most common and most likely answer to this crossword clue is the 5 letter word GUISE
I've seen this crossword clue in Financial Times
G
U
I
S
E
More clues leading to the result GUISE
Buddy explains!
The straight part
We know that "an appearance" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case an appearance = guise.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 GUISE mean?
GUISE noun- Customary way of speaking or acting; fashion, manner, practice (often used formerly in such phrases as "at his own guise"; that is, in his own fashion, to suit himself.)
- External appearance in manner or dress; appropriate indication or expression; garb; shape.
- Misleading appearance; cover, cloak.
- To dress.
- To act as a guiser; to go dressed up in a parade etc.