The most common and most likely answer to this crossword clue is the 7 letter word PULLMAN
I've seen this crossword clue in The Guardian
P
U
L
L
M
A
N
More clues leading to the result PULLMAN
Buddy explains!
The straight part
We know that "What vamp wants to do/coach" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case what vamp wants to do/coach = pullman.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.