Cryptic crossword clue
Complex machinery caught nation’s port out 12

The most common and most likely answer to this crossword clue is the 12 letter word CONTRAPTIONS

I've seen this crossword clue in The Guardian
C
O
N
T
R
A
P
T
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S

Buddy explains!

The straight part
We know that "Complex machinery" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case complex machinery = contraptions.
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 CONTRAPTIONS mean?

CONTRAPTIONS noun
  1. A machine that is complicated and precarious.
  2. Any object.

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