The most common and most likely answer to this crossword clue is the 7 letter word PICKAXE
I've seen this crossword clue in The Daily Telegraph
P
I
C
K
A
X
E
More clues leading to the result PICKAXE
Buddy explains!
The straight part
We know that "that’s groundbreaking" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case that’s groundbreaking = pickaxe.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 PICKAXE mean?
PICKAXE noun- A heavy iron tool with a wooden handle; one end of the head is pointed, the other has a chisel edge.
- To use a pickaxe.