See someone, for the first time lacking in vision, become obsolete (5,4)
I believe the answer is:
blind date
'lacking in vision become obsolete' is the definition.
I can't judge whether this defines the answer.
'see someone for the first time' is the wordplay.
'see someone' becomes 'date' (date is a kind of someone).
'for' means one lot of letters go next to another (I've seen this in other clues).
'the first time' becomes 'blind' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'date' put after 'blind' is 'BLIND DATE'.
Can you help me to learn more?
(Other definitions for blind date that I've seen before include "Social engagement (entered into with one's eyes closed?)" , "Surprise assignation" , "New pairing" , "Bend it, lad (anag)" , "Social appointment with stranger" .)