Mystery writer Macdonald (4)
I believe the answer is:
ross
'mystery writer macdonald' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ross that I've seen before include "Jonathan - - (TV)" , "Diana --, Motown singer" , "Wye town; Antarctic sea" , "-- And Cromarty, former county of Scotland" , "-- Dependency; -- Sea" .)