The most common and most likely answer to this crossword clue is the 11 letter word PROBLEMATIC
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More clues leading to the result PROBLEMATIC
Buddy explains!

The straight part
We know that "Troublesome" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case troublesome = problematic.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 PROBLEMATIC mean?
PROBLEMATIC noun- (chiefly in the plural) A problem or difficulty in a particular field of study.
- Posing a problem; having or suffering from problem(s):
- Only affirming the possibility that a predicate be actualised.