The most common and most likely answer to this crossword clue is the 7 letter word ZAPPING
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Buddy explains!

The straight part
We know that "Depleting" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case depleting = zapping.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 ZAPPING mean?
ZAPPING verb- To make a zap sound.
- To use a remote control to repeatedly change channels on a television.
- To strike (something or someone) with electricity or energy, as by shooting.
- To kill; to eliminate.
- To damage (especially electronics) with electrostatic discharge.
- To heat (something) in a microwave oven.
- To delete or discard (electronic media).
- To further energize or charge (magnetic material).
- The act or result of being zapped.