Mark permitted to see red (7)
I believe the answer is:
scarlet
'red' is the definition.
(I've seen this before)
'mark permitted' is the wordplay.
'mark' becomes 'scar' ('scar' can be a synonym of 'mark'**).
'permitted' becomes 'let' (I've seen this before).
'scar'+'let'='SCARLET'
'to see' is the link.
(Other definitions for scarlet that I've seen before include "Shade of red" , "Cartels (anag.)" , "Clarets (anag.)" , "Bright red of clarets" , "Red colour of clarets" .)