Nameless dead artist's intensely dark shade (5)
I believe the answer is:
umbra
'intensely dark shade' is the definition.
(umbra is a type of shadow)
'nameless dead artist's' is the wordplay.
I cannot really understand how this works, but
'artist' could be 'ra' (Royal Academician, member of Royal Academy of Arts) and 'ra' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for umbra that I've seen before include "Shade, or ghost" , "Shadow's inner region" , "Dark shadow cast by earth in eclipse" , "Area of total shadow" , "dark place" .)