The most common and most likely answer to this crossword clue is the 9 letter word ARTIFICER
I've seen this crossword clue in The Times
A
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More clues leading to the result ARTIFICER
Buddy explains!

The straight part
We know that "Mechanic" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case mechanic = artificer.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 ARTIFICER mean?
ARTIFICER noun- Someone who is skilled in their trade; an artisan.
- An inventor.
- A member of the military who specializes in manufacturing and repairing weapon systems.
- A trickster.
- A savant.