The most common and most likely answer to this crossword clue is the 13 letter word COMPLICATIONS
I've seen this crossword clue in The Daily Telegraph
C
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Buddy explains!

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 COMPLICATIONS mean?
COMPLICATIONS noun- The act or process of complicating.
- The state of being complicated; intricate or confused relation of parts; complexity.
- A person who doesn't fit in with the main scheme of things; an interloper.
- A disease or diseases, or adventitious circumstances or conditions, coexistent with and modifying a primary disease, but not necessarily connected with it.
- A feature beyond basic time display in a timepiece.