Dead artist seen following exercise in shadow (8)
I believe the answer is:
penumbra
'shadow' is the definition.
(I know that penumbra is a class)
'dead artist seen following exercise in' is the wordplay.
'dead' becomes 'numb' (as in a dead arm).
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'seen following' means one lot of letters go next to another.
'exercise' becomes 'pe' (Physical Education).
'in' indicates putting letters inside.
'ra' after 'pe' is 'pera'.
'numb' put into 'pera' is 'PENUMBRA'.
(Other definitions for penumbra that I've seen before include "Area of half shade" , "Ring around sunspot" , "Outer shadow round object" , "Imperfect shadow" , "Shady area" .)