The most common and most likely answer to this crossword clue is the 12 letter word PREPOSSESSED
I've seen this crossword clue in Financial Times
P
R
E
P
O
S
S
E
S
S
E
D
More clues leading to the result PREPOSSESSED
Buddy explains!
The straight part
We know that "Worried" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case worried = prepossessed.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.