The most common and most likely answer to this crossword clue is the 10 letter word WATERTIGHT
I've seen this crossword clue in The Guardian
W
A
T
E
R
T
I
G
H
T
More clues leading to the result WATERTIGHT
- Drunk’s after a non-alcoholic drink — perfect
- Liquid and what it can't make one for sure
- With target organised, allowing no escape
- What could be drunk twice? That’s irrefutable
- Two sorts of hose, almost flawless
- Certain to get drunk on Adam’s ale
- Sound drunk after refreshing drink
- Bulletproof with target moving
- Without doubt, this won’t get you that!
- Unsinkable Jonathan Ross evokes spirit of Spooner in claiming he ‘trained that woman correctly’
Buddy explains!
The straight part
We know that "Certain" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case certain = watertight.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 WATERTIGHT mean?
WATERTIGHT adjective- So tightly made that water cannot enter or escape.
- So devised or planned as to be impossible to defeat, evade or nullify.