Period shown in Northanger Abbey (3)
I believe the answer is:
era
'period' is the definition.
(era is a kind of period)
'shown in northanger abbey' is the wordplay.
'shown in' says the answer is hidden in the clue.
'ERA' is hidden within 'northanger abbey'.
(Other definitions for era that I've seen before include "generation, maybe" , "Important time" , "Epoch, period" , "Specific time" , "Long period of time" .)