The most common and most likely answer to this crossword clue is the 9 letter word RUN-UP[P]
R
U
N
-
U
P
[
P
]
Buddy explains!
The straight part
We know that "Approach" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case approach = run-up[p].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.