Inadvertent mistake concerning vision (9)
I believe the answer is:
oversight
'inadvertent mistake' is the definition.
(something somebody overlooked)
'concerning vision' is the wordplay.
'concerning' becomes 'over' (both can mean relating to).
'vision' becomes 'sight' (synonyms).
'over'+'sight'='OVERSIGHT'
(Other definitions for oversight that I've seen before include "Mistake resulting from inattention" , "Neglect" , "Failure to notice - blunder" , "Supervisor's charged with this" , "Shot giver due to unintentional omission" .)