The most common and most likely answer to this crossword clue is the 6 letter word BUNGLE
I've seen this crossword clue in The Daily Telegraph
B
U
N
G
L
E
More clues leading to the result BUNGLE
Buddy explains!

The straight part
We know that "gross mismanagement" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case gross mismanagement = bungle.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 BUNGLE mean?
BUNGLE noun- A botched or incompetently handled situation.
- To botch up, bumble or incompetently perform a task; to make or mend clumsily; to manage awkwardly.