Endless alarm - thats what the wound leaves behind (4)
I believe the answer is:
scar
'what the wound leaves behind' is the definition.
I know that 'wound' relates to this answer.
'endless alarm' is the wordplay.
'endless' means to remove the last letter.
'alarm' becomes 'scare' (I've seen this before).
'scare' with its final letter taken off is 'SCAR'.
'thats' is the link.
Can you help me to learn more?
(Other definitions for scar that I've seen before include "Steep rock - blemish" , "area of wound" , "Mark from a wound left on the skin" , "Skin mark; bare crag" , "Visible mark of healing" .)