The books a heartless dog looks around for? (7)
I believe the answer is:
ledgers
'the books' is the definition.
('ledger' can be a synonym of 'book')
'looks around for?' is the wordplay.
'looks' becomes 'leers' (leer is a kind of look).
'around' indicates putting letters inside.
'for?' becomes 'dg' (I am not sure about this - if you are sure you should believe this answer much more).
'leers' placed around 'dg' is 'LEDGERS'.
'a heartless dog' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for ledgers that I've seen before include "Account-books" , "Books listing commercial transactions" , "Account books" , "Books of accounts" , "old spreadsheets" .)