Major books hoarded by economist briefly (7)
I believe the answer is:
keynote
'major' is the definition.
(thesaurus)
'books hoarded by economist briefly' is the wordplay.
'books' becomes 'ot' (Old Testament).
'hoarded by' is an insertion indicator (hoard can mean to hold onto).
'economist' becomes 'keynes' (Keynes is an example).
'briefly' means to remove the last letter.
'keynes' with its last letter taken off is 'keyne'.
'ot' put inside 'keyne' is 'KEYNOTE'.
(Other definitions for keynote that I've seen before include "One tyke (anag)" , "Central theme" , "Speech that sets the tone of a conference" , "The central speech of a conference" , "Prevailing tone or idea of a speech" .)