The most common and most likely answer to this crossword clue is the 6 letter word FINDER
I've seen this crossword clue in The Guardian
F
I
N
D
E
R
More clues leading to the result FINDER
Buddy explains!
The straight part
We know that "one discovers" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one discovers = finder.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 FINDER mean?
FINDER noun- One who finds or discovers something.
- An optical device, such as a viewfinder, used to locate a target or other object of interest