The most common and most likely answer to this crossword clue is the 9 letter word UNSKILLED
I've seen this crossword clue in The Guardian
U
N
S
K
I
L
L
E
D
Buddy explains!

The straight part
We know that "with no training necessary" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case with no training necessary = unskilled.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 UNSKILLED mean?
UNSKILLED adjective- Of a person or workforce: not having a skill or technical training.
- Of a job: not requiring skill or training.
- Of a made object: inexpertly made or showing a lack of skill.