The most common and most likely answer to this crossword clue is the 6 letter word IMPAIR
I've seen this crossword clue in The Times
I
M
P
A
I
R
More clues leading to the result IMPAIR
- Do damage to India with Middlesex’s opening duo
- Expression on demon creating damage
- One married couple weaken
- Spoil naughty child, 10
- Rascal to disclose damage
- One million and two hurt
- This person's item in hamper
- Spoil the atmosphere, backing one up to no good
- “Like to good angels, nothing can —: / ’Tis less grief to be foul, than to have been fair”
- Compiler’s two ducks causing damage
Buddy explains!

The straight part
We know that "damage" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case damage = impair.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 IMPAIR mean?
IMPAIR verb- To weaken; to affect negatively; to have a diminishing effect on.
- To grow worse; to deteriorate.
- Not fit or appropriate; unsuitable.