The most common and most likely answer to this crossword clue is the 6 letter word SEEMLY
I've seen this crossword clue in The Daily Telegraph
S
E
E
M
L
Y
More clues leading to the result SEEMLY
- Appropriate picture – source of light in heavens
- Suitable space found in Spain’s capital city
- Notice surprised expression around lecturer of decent character
- Look largely empty but handsome
- Becoming on the face of it neither popular nor good
- Becoming wily when penning English, this writer flipped
- Energy and dash in furtive meet
- Notice man with lady unnoticed — that’s proper!
Buddy explains!

The straight part
We know that "Becoming" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case becoming = seemly.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 SEEMLY mean?
SEEMLY adjective- (of behavior) Appropriate; suited to the occasion or purpose; becoming.
- Appropriately, fittingly.