The most common and most likely answer to this crossword clue is the 4 plus 2 plus 4 letter word HAVE IT MADE
H
A
V
E
I
T
M
A
D
E
More clues leading to the result HAVE IT MADE
Buddy explains!
The straight part
We know that "Be assured of success in bespoke tailoring" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case be assured of success in bespoke tailoring = have it made.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.