The most common and most likely answer to this crossword clue is the 8 letter word BORROWER
B
O
R
R
O
W
E
R
More clues leading to the result BORROWER
- Not entirely natural athlete, one may be found in the library
- A tiny thief returned to do over one pulling blade?
- Plunder picked up by boater? One intends to return things
- She has loan of drill, welcoming din
- Library user, maybe one claiming iPod found under floorboards?
- Person withdrawing library books, one with 13 perhaps?
Buddy explains!

The straight part
We know that "A tiny thief" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a tiny thief = borrower.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 BORROWER mean?
BORROWER noun- One who borrows.