Author's old set of books in prominent position (6)
I believe the answer is:
capote
'author's' is the definition.
(I've seen this before)
'books in prominent position' is the wordplay.
'books' becomes 'OT' (abbreviation for Old Testament).
'in' means one lot of letters goes inside another.
'prominent position' becomes 'cape' (I am not sure about this - if you are sure you should believe this answer much more).
'ot' placed inside 'cape' is 'CAPOTE'.
'old set of' acts as a link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for capote that I've seen before include "Truman perhaps" , "Truman - - , novelist" , "Truman --, US author" , "Author of Breakfast at Tiffany's, d. 1984" , "US author - long cloak" .)