The most common and most likely answer to this crossword clue is the 16 letter word NON-INTERVENTION
I've seen this crossword clue in The Guardian
N
O
N
-
I
N
T
E
R
V
E
N
T
I
O
N
Buddy explains!
The straight part
We know that "laissez-faire policy" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case laissez-faire policy = non-intervention.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 NON-INTERVENTION mean?
NON-INTERVENTION noun- The policy of a state of not intervening in the domestic affairs of another.