Ape a famous historian (6)
I believe the answer is:
gibbon
I believe this clue is a double definition.
'ape' is the first definition.
(I know that gibbon is a type of lesser ape)
'a famous historian' is the second definition.
(Edward Gibbon, 1737-1794)
(Other definitions for gibbon that I've seen before include "Member of the ape family" , "Animal" , "an eighteenth-century author" , "MONKEY" , "Large tailless ape" .)