The most common and most likely answer to this crossword clue is the 12 letter word GUARDIANSHIP
I've seen this crossword clue in The Guardian
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More clues leading to the result GUARDIANSHIP
Buddy explains!

The straight part
We know that "Responsibility for safety" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case responsibility for safety = guardianship.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 GUARDIANSHIP mean?
GUARDIANSHIP noun- The office or position of one acting as a guardian or conservator, especially in a legal capacity.