Nuts about raw beginner's sketch (5)
I believe the answer is:
draft
'sketch' is the definition.
(draft is a kind of sketch)
'nuts about raw beginner's' is the wordplay.
'nuts' becomes 'daft' ('daft' can be a synonym of 'nuts'**).
'about' means one lot of letters goes inside another.
'beginner's' says to take the initial letters (I've seen 'beginners' mean this).
The first letter of 'raw' is 'r'.
'daft' enclosing 'r' is 'DRAFT'.
(Other definitions for draft that I've seen before include "Written plan" , "Current of air or preliminary sketch" , "Bank payment order" , "form of conscription" , "Preliminary version or sketch" .)