Author of The Three Musketeers (5)
I believe the answer is:
dumas
'author of the three musketeers' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for dumas that I've seen before include "Musketeers writer" , "Alexandre ---, wrote Count of Monte Cristo" , "French pair who wrote" , "Author of The Three Musketeers" , "French novelist" .)