The most common and most likely answer to this crossword clue is the 7 letter word THYSELF
I've seen this crossword clue in The Times
T
H
Y
S
E
L
F
More clues leading to the result THYSELF
Buddy explains!

The straight part
We know that "Personally you once" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case personally you once = thyself.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 THYSELF mean?
THYSELF pronoun- Yourself (as the object of a verb or preposition or as an intensifier); reflexive case of thou