The most common and most likely answer to this crossword clue is the 7 letter word SHELVES
I've seen this crossword clue in The Daily Telegraph
S
H
E
L
V
E
S
Buddy explains!
The straight part
We know that "Puts back/books on these?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case puts back/books on these? = shelves.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 SHELVES mean?
SHELVES noun- A flat, rigid structure, fixed at right angles to a wall or forming a part of a cabinet, desk etc., and used to support, store or display objects.
- The capacity of such an object
- A projecting ledge that resembles such an object.
- A reef, shoal or sandbar.
- To place on a shelf.
- To set aside; to quit or postpone.
- To furnish with shelves.
- To take (drugs) by anal or vaginal insertion.
- To have sex with.
- To slope; to incline; to form into shelves.