Clue: Sight defect produced by excessive work starts to impair academic (9)
Answer: HYPEROPIA
Explanation: Definition: Sight defect
 HYPER-(prefix indicating "excessive"/above normal) + OP(abbrev. for "opus", a musical or literary piece of work) + **1st letters, respectively, of**(starts to) "impair academic".
Defn: …, specifically, farsightedness.