Bill polite about set of books (6)
I believe the answer is:
notice
'bill' is the definition.
(synonyms)
'polite about set of books' is the wordplay.
'polite' becomes 'nice'.
'about' is an insertion indicator.
'set of books' becomes 'ot' (I've seen this in other clues).
'nice' enclosing 'ot' is 'NOTICE'.
(Other definitions for notice that I've seen before include "Become aware of; review" , "Sign posted in a public place" , "Observe, percieve" , "Remark upon; small advertisement" , "Advance information" .)