Possible outcome of reading English with OK tutor (9)
I believe the answer is:
eyestrain
'possible outcome of reading' is the definition.
'english with ok tutor' is the wordplay.
'english' becomes 'e' (abbreviation).
'with' means one lot of letters go next to another.
'ok' becomes 'yes' (I've seen this before).
'tutor' becomes 'train' (I've seen this before).
'e'+'yes'+'train'='EYESTRAIN'
(Other definitions for eyestrain that I've seen before include "Optical irritation or tiredness" , "Difficulty in sight" , "unpleasant condition" , "Discomfort of sightseers" , "Tension on the visual organ" .)