The most common and most likely answer to this crossword clue is the 4 plus 2 plus 4 plus 2 letter word TAKE IT FROM ME
I've seen this crossword clue in The Daily Telegraph
T
A
K
E
I
T
F
R
O
M
M
E
More clues leading to the result TAKE IT FROM ME
Buddy explains!
The straight part
We know that "You’d better believe that" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case you’d better believe that = take it from me.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.