The most common and most likely answer to this crossword clue is the 9 letter word ARRIVISTE
I've seen this crossword clue in The Daily Telegraph
A
R
R
I
V
I
S
T
E
More clues leading to the result ARRIVISTE
- Top tip for real trivia nuts, including son heading for Eggheads — he’s aiming high
- A striver, I fancy?
- Upstart’s rare visit arranged
- Upstart lawyer, knowing no limits, penning Volume One
- Johnny-come-lately is on time, come over
- Social climber Carrie’s endless struggle to hide Boris’s temperament, conclusively
- Climber‘s current view leaving area in rare ground
- Social climber‘s rare visit abroad
- Parvenu‘s rare visit irritated
Buddy explains!

The straight part
We know that "A striver, I" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a striver, i = arriviste.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 ARRIVISTE mean?
ARRIVISTE noun- An upstart or newcomer; nouveau riche; parvenu; an ambitious, brash or arrogant person who has yet to integrate with his or her new social group.