One getting back from post-war celebration in rage (7)
I believe the answer is:
avenger
'one getting back' is the definition.
(someone who gets back at others)
'post-war celebration in rage' is the wordplay.
'post war celebration' becomes 've' (I can't explain this - if you can you should give a lot more credence to this answer).
'in' indicates putting letters inside.
'rage' becomes 'anger' (I've seen this in another clue).
've' inserted into 'anger' is 'AVENGER'.
'from' is the link.
Can you help me to learn more?
(Other definitions for avenger that I've seen before include "party retaliating" , "One who seeks or obtains satisfaction for injury" , "Fury results" , "Mrs Peel?" , "Inflicter of retribution" .)