The most common and most likely answer to this crossword clue is the 3 plus 5 letter word OLD TIMER
I've seen this crossword clue in The Daily Telegraph
O
L
D
T
I
M
E
R
More clues leading to the result OLD TIMER
Buddy explains!
The straight part
We know that "Veteran" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case veteran = old timer.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 OLD TIMER mean?
OLD TIMER noun- One who has been around for a long time or has a great deal of experience; a veteran.