The most common and most likely answer to this crossword clue is the 7 letter word SHAKIER
I've seen this crossword clue in The Daily Telegraph
S
H
A
K
I
E
R
Buddy explains!
The straight part
We know that "One’s more uncertain on this ground" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one’s more uncertain on this ground = shakier.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 SHAKIER mean?
SHAKIER adjective- Shaking or trembling.
- Nervous, anxious.
- (of wood) Full of shakes or cracks; cracked.
- Easily shaken; tottering; unsound.
- Wavering; undecided.