The most common and most likely answer to this crossword clue is the 5 plus 5 letter word ENTRY LEVEL
I've seen this crossword clue in The Guardian
E
N
T
R
Y
L
E
V
E
L
Buddy explains!
The straight part
We know that "ground floor" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case ground floor = entry level.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 ENTRY LEVEL mean?
ENTRY LEVEL adjective- Simple enough to be appropriate to an inexperienced person, or to someone who does not need advanced features.