Small auto, crimson, permanently marked (7)
I believe the answer is:
scarred
'marked' is the definition.
('scar' can be a synonym of 'mark')
'small auto crimson permanently' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'auto' becomes 'car' (synonyms).
'crimson permanently' becomes 'red' (synonyms. I am not sure about the 'permanently' bit.).
's'+'car'+'red'='SCARRED'
Can you help me to learn more?
(Other definitions for scarred that I've seen before include "Blemished" , "Marked (by wound)" , "Bearing the marks of wounds" , "bearing evidence of injury" , "Flawed" .)