Afterwards alter formation (5)
I believe the answer is:
later
'afterwards' is the definition.
(I know that afterwards can be written as later)
'alter formation' is the wordplay.
'formation' is an anagram indicator.
'alter' with letters rearranged gives 'LATER'.
(Other definitions for later that I've seen before include "bye" , "Following" , "after an interval" , "at a future date" , "Tardier" .)