Mark from a wound allowed to become red (7)
I believe the answer is:
scarlet
'red' is the definition.
(I've seen this before)
'mark from a wound allowed' is the wordplay.
'mark from a wound' becomes 'scar' (I've seen this before).
'allowed' becomes 'let' (I've seen this before).
'scar'+'let'='SCARLET'
'to become' acts as a link.
(Other definitions for scarlet that I've seen before include "bloody?" , "Shade of red" , "Clarets (anag.)" , "Brilliant red colour" , "Murderer" .)