The most common and most likely answer to this crossword clue is the 10 letter word PERSEVERES
I've seen this crossword clue in The Times
P
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R
S
E
V
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More clues leading to the result PERSEVERES
Buddy explains!
The straight part
We know that "Is determined" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case is determined = perseveres.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 PERSEVERES mean?
PERSEVERES verb- To persist steadfastly in pursuit of an undertaking, task, journey, or goal, even if hindered by distraction, difficulty, obstacles, or discouragement.
- To stay constant; to continue in a certain state; to remain.