Clue: Sober English teacher circles something hard to miss (6)
Answer: SITTER
Explanation: Definition: something hard to miss
 [ TT(abbrev. for "tee-total"/sober by abstaining from alcohol) + E(abbrev. for "English") ] **contained in**(… circles) SIR(what schoolboys might call their male teacher).
Defn: …, such as an easy goal in football or an easy catch in cricket.