A multitude some author described (5)
I believe the answer is:
horde
'a multitude' is the definition.
(I know that horde is a type of multitude)
'some author described' is the wordplay.
'some' indicates the answer is hidden within the clue (some parts of the word are used).
'HORDE' is hidden within 'author described'.
(Other definitions for horde that I've seen before include "Migratory tribe; army" , "Great crowd" , "Nomadic army" , "Large group of people" , "A moving crowd" .)