A very long time in some village school (4)
I believe the answer is:
ages
'a very long time' is the definition.
(ages can informally mean a long period)
'in some village school' is the wordplay.
'in' indicates a hidden word.
'AGES' is hidden within 'some village school'.
(Other definitions for ages that I've seen before include "Donkey's years" , "Matures" , "Aeons" , "Gets older" , "Historic periods or prolonged time" .)