The most common and most likely answer to this crossword clue is the 7 letter word DILUTES
I've seen this crossword clue in The Guardian
D
I
L
U
T
E
S
More clues leading to the result DILUTES
Buddy explains!
The straight part
We know that "weakening" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case weakening = dilutes.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 DILUTES mean?
DILUTES noun- An animal having a lighter-coloured coat than is usual.
- To make thinner by adding solvent to a solution, especially by adding water.
- To weaken, especially by adding a foreign substance.
- To cause the value of individual shares or the stake of a shareholder to decrease by increasing the total number of shares.
- To become attenuated, thin, or weak.