The most common and most likely answer to this crossword clue is the 5 plus 3 plus 6 letter word BREAK NEW GROUND
I've seen this crossword clue in Financial Times
B
R
E
A
K
N
E
W
G
R
O
U
N
D
More clues leading to the result BREAK NEW GROUND
Buddy explains!
The straight part
We know that "Harrow for the first time/to be innovative" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case harrow for the first time/to be innovative = break new ground.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.