Book compiled by Neil Cox (7)
I believe the answer is:
lexicon
'book' is the definition.
(I know that lexicon is a type of book)
'compiled by neil cox' is the wordplay.
'compiled' is an anagram indicator.
'by' is a charade indicator (letters next to each other).
'neil' put after 'cox' is 'coxneil'.
'coxneil' anagrammed gives 'LEXICON'.
(Other definitions for lexicon that I've seen before include "Book of words" , "it has a lot of words" , "reference work?" , "(Classical) dictionary" , "Dictionary of terms" .)