Mistake concerning vision (9)
I believe the answer is:
oversight
'mistake' is the definition.
(I know that oversight is a type of mistake)
'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 "Got shiver due to forgetfulness" , "Failure to notice - supervision" , "Slip-up" , "Management" , "act of negligence" .)