Vision close to usual standard (5)
I believe the answer is:
ideal
'standard' is the definition.
(as in an ideal or optimal standard)
'vision close to usual' is the wordplay.
'vision' becomes 'idea' (I've seen this in another clue).
'close to' suggests the final letters (the close/ending of).
The last letter of 'usual' is 'l'.
'idea'+'l'='IDEAL'
(Other definitions for ideal that I've seen before include "Something that one hopes to attain" , "Optimum" , "Just the ticket" , "example" , "Model of ethical behaviour" .)