The most common and most likely answer to this crossword clue is the 2 plus 4 plus 3 plus 6 letter word BE ONES OWN MASTER
I've seen this crossword clue in The Times
B
E
O
N
E
S
O
W
N
M
A
S
T
E
R
Buddy explains!
The straight part
We know that "Maintain independence /advance oneself autodidactically" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case maintain independence /advance oneself autodidactically = be ones own master.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.