Amend sketch showing two features of skin abrasion? (6)
I believe the answer is:
redraw
'amend sketch' is the definition.
(to draw or sketch again)
I can't explain the rest of the clue.
(Other definitions for redraw that I've seen before include "plan afresh" , "Pick over" , "Design again" , "Delineate again" , "Sketch again" .)