The most common and most likely answer to this crossword clue is the 7 letter word EPIGEAL
I've seen this crossword clue in The Times
E
P
I
G
E
A
L
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The straight part
We know that "On the ground" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case on the ground = epigeal.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 EPIGEAL mean?
EPIGEAL adjective- Living near the surface of the ground
- (of a cotyledon) Emerging above the surface of the ground after being germinated