The most common and most likely answer to this crossword clue is the 10 letter word FEARLESSLY
I've seen this crossword clue in The Times
F
E
A
R
L
E
S
S
L
Y
Buddy explains!
The straight part
We know that "with plenty of grit" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case with plenty of grit = fearlessly.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 FEARLESSLY mean?
FEARLESSLY adverb- In a fearless manner; without fear.