Deep cut (4)
'deep cut' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for gash that I've seen before include "surplus to requirements" , "Jagged cut" , "Deep open cut" , "Open wound" , "Long deep slash" .)
(Other definitions for laceration that I've seen before include "wound" , "cutting" , "Tearing (of skin)" , "rent" , "Tear" .)
(Other definitions for incision that I've seen before include "Cut made surgically into the body" , "Cut as made with surgeon's knife" , "A surgical cut into the body" , "Surgical ten across" , "Cut, gash" .)