The most common and most likely answer to this crossword clue is the 5 letter word LETHE
I've seen this crossword clue in The Times
L
E
T
H
E
More clues leading to the result LETHE
- Woman's last to surface — drink has a profound effect here?
- Water underground comes from toilet here
- Flower, deep in the ground, no forget-me-not!
- Do what! Mountain of rubbish going up river
- After half a pill he attains oblivion
- Underground flow of water coming from toilet here
- Allow that man to find oblivion
- Component of diethyl ether caused memory loss when drunk
Buddy explains!
The straight part
We know that "drink has a profound effect here" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case drink has a profound effect here = lethe.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.