The most common and most likely answer to this crossword clue is the 6 plus 1 letter word LINEAR B
I've seen this crossword clue in Independent
L
I
N
E
A
R
B
More clues leading to the result LINEAR B
Buddy explains!
The straight part
We know that "close by in library (6,1)" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case close by in library (6,1) = linear b.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.