Long time inside after aggression (3)

I believe the answer is:

era

'long time' is the definition.
(a long period of time)

'inside after aggression' is the wordplay.
'inside' says the answer is hidden in the clue.
'ERA' is hidden within 'after aggression'.

(Other definitions for era that I've seen before include "Geological age" , "Distinct period in history" , "Long historical period" , "Memorable period" , "US equality law" .)

I've seen this clue in The Sun.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.