Crude sketch, not the first (3)
I believe the answer is:
raw
'crude' is the definition.
('raw' can be a synonym of 'crude')
'sketch not the first' is the wordplay.
'sketch' becomes 'draw' (I've seen this before).
'not the first' means to remove the first letter.
'draw' with its first letter taken away is 'RAW'.
(Other definitions for raw that I've seen before include "Inexperienced in war (3)" , "not yet ready to eat" , "Uncooked or crude" , "Unprocessed" , "Damp and chilly" .)