... finally shot with huge gun afterwards (4)
I believe the answer is:
then
'afterwards' is the definition.
(I've seen this before)
'finally shot with huge gun' is the wordplay.
'finally' says to take the final letters.
The final letters of 'shot with huge gun' are 'THEN'.
(Other definitions for then that I've seen before include "soon?" , "Once upon a time" , "Subsequently - previously" , "Afterwards - as a result" , "At that time; next" .)