Artist’s Sleep Activity/Mark Twain’s Head (9)
I believe the answer is:
rembrandt
'artist's' is the definition.
(Rembrandt is an example)
'sleep activitymark twain's head' is the wordplay.
'sleep' becomes 'rem' (abbreviation for Rapid Eye Movement).
'activitymark' becomes 'brand' (I can't explain this - if you can you should give a lot more credence to this answer).
'head' says to take the initial letters.
The initial letter of 'twains' is 't'.
'rem'+'brand'+'t'='REMBRANDT'
Can you help me to learn more?
(Other definitions for rembrandt that I've seen before include "Influential Dutch artist" , "Dutch painter, d. 1669" , "Dutch painter, 1606-69" , "'Night Watch' painter" , "One notably exhibited" .)