The most common and most likely answer to this crossword clue is the 6 plus 4 letter word GRANNY KNOT
I've seen this crossword clue in The Sunday Telegraph
G
R
A
N
N
Y
K
N
O
T
More clues leading to the result GRANNY KNOT
Buddy explains!

The straight part
We know that "Bad way to tie" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bad way to tie = granny knot.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.