The French boy’s time at school (6)
I believe the answer is:
lesson
'time at school' is the definition.
'the french boy's' is the wordplay.
'the french' becomes 'les' (les is the in french).
'boy' becomes 'son' ('son' can be a synonym of 'boy'**).
'les'+'son'='LESSON'
(Other definitions for lesson that I've seen before include "15 down period" , "See 1" , "Seminar" , "Sermon or example" , "Single period of instruction" .)