Doctor coped nicely, given a reference book (12)
I believe the answer is:
encyclopedia
'reference book' is the definition.
(I know that encyclopedia is a type of reference book)
'doctor coped nicely given a' is the wordplay.
'doctor' is an anagram indicator.
'given' is a charade indicator (letters next to each other).
'coped'+'nicely'='copednicely'
'copednicely' is an anagram of 'encyclopedi'.
'encyclopedi'+'a'='ENCYCLOPEDIA'
(Other definitions for encyclopedia that I've seen before include "Reference book" , "Book of knowledge" , "Reference work" .)