Do some artwork – in the blue, lacking detail (7)
I believe the answer is:
sketchy
'lacking detail' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for sketchy that I've seen before include "Superficial" , "first draft" , "Incomplete; rough" , "Imperfect" , "Imprecise" .)