The most common and most likely answer to this crossword clue is the 8 letter word ROTOTILL
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Buddy explains!

The straight part
We know that "do some gardening" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case do some gardening = rototill.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 ROTOTILL mean?
ROTOTILL verb- To break up and turn soil using a rototiller.
- To make extensive and pervasive changes to a piece of code without altering its functionality.