Copier a chap uses in novel (10)
I believe the answer is:
amanuensis
'copier' is the definition.
(thesaurus)
'a chap uses in novel' is the wordplay.
'chap' becomes 'man' (I've seen this before**).
'novel' is an anagram indicator.
'uses'+'in'='usesin'
'usesin' is an anagram of 'uensis'.
'a'+'man'+'uensis'='AMANUENSIS'
(Other definitions for amanuensis that I've seen before include "One assisting writer" , "Secretary" , "who may work with dictator?" , "Literary assistant - scribe" , "dictator's collaborator, perhaps" .)