It’s ending in aftermath (4)
I believe the answer is:
term
'it's ending' is the definition.
(term can mean the end of something)
'in aftermath' is the wordplay.
'in' indicates a hidden word.
'TERM' is hidden within 'aftermath'.
(Other definitions for term that I've seen before include "Fixed period of time" , "Limited period; school session" , "Limited period of time" , "School time; word" , "expected time of delivery" .)