Final words defending foul antics (6)
I believe the answer is:
pranks
'antics' is the definition.
(I know this)
'final words defending foul' is the wordplay.
'final words' becomes 'ps' (I can't justify this - if you can you should believe this answer much more).
'defending' means one lot of letters goes inside another (inserted letters are defended).
'foul' becomes 'rank' (both can mean rotten).
'ps' placed around 'rank' is 'PRANKS'.
Can you help me to learn more?
(Other definitions for pranks that I've seen before include "Tricks" , "Jokes, capers" , "Practical jokes, pieces of mischief" , "Tricky things to play" .)