The most common and most likely answer to this crossword clue is the 5 letter word HOLED
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More clues leading to the result HOLED
Buddy explains!

The straight part
We know that "no longer watertight" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case no longer watertight = holed.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 HOLED mean?
HOLED verb- To make holes in (an object or surface).
- (by extension) To destroy.
- To go into a hole.
- To drive into a hole, as an animal, or a billiard ball or golf ball.
- To cut, dig, or bore a hole or holes in.
- Having one or more holes.