The most common and most likely answer to this crossword clue is the 10 letter word IMPASSABLE
I've seen this crossword clue in The Times
I
M
P
A
S
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A
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Buddy explains!

The straight part
We know that "If so, there's no getting over it" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case if so, there's no getting over it = impassable.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 IMPASSABLE mean?
IMPASSABLE adjective- (of a route, terrain, etc.) Incapable of being passed over, crossed, or negotiated.
- (of an obstacle) Incapable of being overcome or surmounted.
- (of currency) Not usable as legal tender.