Book shelf has little resistance (6)
I believe the answer is:
ledger
'book' is the definition.
('ledger' can be a synonym of 'book')
'shelf has little resistance' is the wordplay.
'shelf' becomes 'ledge' ('ledge' can be a synonym of 'shelf').
'has' says to put letters next to each other.
'little' suggests taking the first letters.
The initial letter of 'resistance' is 'r'.
'ledge'+'r'='LEDGER'
(Other definitions for ledger that I've seen before include "Heath -, Australian actor" , "In which accounts are entered" , "Accounts journal" , "Old-fashioned heavy accounts book" , "Book-keeper's book" .)