Stab (5)
'stab' is the definition.
(I know that stab can be written as knife)
This is all the clue.
(Other definitions for knife that I've seen before include "Potential weapon" , "Sharp tool" , "Piece of cutlery" , "Cut" , "Attack" .)
'stab' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for pierce that I've seen before include "Thrust" , "Skewer; run through" , "Cavalry sword" , "Possibly drill" , "Puncture or penetrate" .)