Accounts book not right for shelf (5)
I believe the answer is:
ledge
'for shelf' is the definition.
(synonyms)
'accounts book not right' is the wordplay.
'accounts book' becomes 'ledger' (I've seen this in another clue).
'not' is a deletion indicator.
'right' becomes 'r' (common abbreviation).
'ledger' with 'r' taken out is 'LEDGE'.
(Other definitions for ledge that I've seen before include "Shelf-life projection" , "Sill" , "Rock shelf" , "Narrow shelf, often attached to window" , "Projecting ridge on a mountain" .)