The most common and most likely answer to this crossword clue is the 3 plus 2 plus 3 letter word ONE OR TWO
I've seen this crossword clue in The Times
O
N
E
O
R
T
W
O
Buddy explains!
The straight part
We know that "Not a lot /choice of platform at a small station?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case not a lot /choice of platform at a small station? = one or two.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.