Great man relaxed with a new novel (9)
I believe the answer is:
alexander
'great man' is the definition.
(Alexander the Great)
'relaxed with a new novel' is the wordplay.
'with' means one lot of letters go next to another.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'novel' is an anagram indicator (letters in a new or novel order).
'relaxed'+'a'+'n'='relaxedan'
'relaxedan' is an anagram of 'ALEXANDER'.
(Other definitions for alexander that I've seen before include "Macedon's "great" king, d. 323 BC" , "Great Greek military commander" , "Macedonian conqueror of Greece" , "band-leader" , "Conquering king of Macedonia" .)