The most common and most likely answer to this crossword clue is the 7 letter word UNAIDED
I've seen this crossword clue in The Guardian
U
N
A
I
D
E
D
Buddy explains!
The straight part
We know that "All by oneself/helpless" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case all by oneself/helpless = unaided.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 UNAIDED mean?
UNAIDED adjective- Without the help, aid or assistance of someone or something.