The most common and most likely answer to this crossword clue is the 6 letter word LOGGIA
I've seen this crossword clue in Independent
L
O
G
G
I
A
More clues leading to the result LOGGIA
- Register those in the vanguard in Germany in art gallery
- Reported one renting room in arcade
- Gallery lost half of Caravaggio works
- Record US soldier by area in arcade
- Insensitive person, soldier at front of a covered arcade
- Left with old goods? One answer could be arcade
- Soldier in gaol confused by open gallery
- Gigolo, dropping a ring, running to a gallery
- Journal, good one, on opening of art gallery
- Trouble over drinking spirit around midnight in open-sided gallery
Buddy explains!

The straight part
We know that "Gallery" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case gallery = loggia.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 LOGGIA mean?
LOGGIA noun- A roofed, open gallery, usually on an upper level.