The most common and most likely answer to this crossword clue is the 4 plus 3 plus 5 letter word JUMP THE QUEUE
I've seen this crossword clue in Financial Times
J
U
M
P
T
H
E
Q
U
E
U
E
More clues leading to the result JUMP THE QUEUE
Buddy explains!
The straight part
We know that "Dishonestly take position as head waiter?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dishonestly take position as head waiter? = jump the queue.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.