The most common and most likely answer to this crossword clue is the 5 letter word FATED
I've seen this crossword clue in The Sunday Telegraph
F
A
T
E
D
More clues leading to the result FATED
Buddy explains!
The straight part
We know that "that’s bound" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case that’s bound = fated.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.
What does FATED mean?
FATED verb- To foreordain or predetermine, to make inevitable.
- Foreordained, predetermined, established in advance by fate.