The most common and most likely answer to this crossword clue is the 9 letter word DISABLING
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More clues leading to the result DISABLING
Buddy explains!

The straight part
We know that "Making feeble" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case making feeble = disabling.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 DISABLING mean?
DISABLING verb- To render unable; to take away an ability of, as by crippling.
- (chiefly of a person) To impair the physical or mental abilities of; to cause a serious, permanent injury.
- To deactivate, to make inoperational (especially of a function of an electronic or mechanical device).