The most common and most likely answer to this crossword clue is the 8 letter word UPSTAIRS
I've seen this crossword clue in Financial Times
U
P
S
T
A
I
R
S
More clues leading to the result UPSTAIRS
- Second USA trip fresh in the mind
- Worried parachutists chat away on the first floor
- Cook puts on fancy manners away from the servants’ quarters
- Mentally puts off with displays of affectation
- Higher level in the mind
- Above us, as trip unfolded
- Rap suits comic mentally
- Order as purist on another level?
- Dicky puts tunes inside one’s head
- Flight destination
Buddy explains!

The straight part
We know that "on the first floor" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case on the first floor = upstairs.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 UPSTAIRS mean?
UPSTAIRS noun- An upper storey.
- Located on a higher floor or level of a building.
- Pertaining to a pitched ball that is high, and usually outside the strike zone.
- Up the stairs; on a higher floor or level.
- In the brain or mind.
- In heaven, especially with regard to where a deity might be found.