The most common and most likely answer to this crossword clue is the 8 letter word SENILITY
I've seen this crossword clue in The Guardian
S
E
N
I
L
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Y
More clues leading to the result SENILITY
Buddy explains!

The straight part
We know that "a hazard of old age/a hazard of old age" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a hazard of old age/a hazard of old age = senility.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 SENILITY mean?
SENILITY noun- Senescence; the bodily and mental deterioration associated with old age.
- The losing of memory and reason due to senescence.
- An elderly, senile person.