The most common and most likely answer to this crossword clue is the 5 plus 8 letter word HEATH ROBINSON
I've seen this crossword clue in Financial Times
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More clues leading to the result HEATH ROBINSON
- Absurdly elaborate waste containers in airport cut leg
- Sadly, her noon habits can be absurdly complex
- Ludicrously complex Briton, he has moved on
- Oddly ingenious PM’s working to engage crime-fighting assistant
- Wild terrain bird occupies shown by quirky illustrator
- Ambassador excited by special order in hotel that’s ridiculously complicated
- Ridiculous man excitedly beating boy around home
- Cartoonist husband in the bar, soon worse for wear
- Ludicrously complex alliance of former British and Irish premiers
- Hard on the brain, so complicated
Buddy explains!
The straight part
We know that "Ludicrously complex" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case ludicrously complex = heath robinson.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.