The most common and most likely answer to this crossword clue is the 2 plus 3 plus 2 plus 1 plus 3 plus 3 letter word AS FAR AS I CAN SEE
I've seen this crossword clue in Financial Times
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More clues leading to the result AS FAR AS I CAN SEE
Buddy explains!
The straight part
We know that "That’s the extent of my vision/to the best of my knowledge" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case that’s the extent of my vision/to the best of my knowledge = as far as i can see.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.