Follow petition on case of extradition (5)
I believe the answer is:
ensue
'follow' is the definition.
(ensue can mean to follow or happen as a result)
'petition on case of extradition' is the wordplay.
'petition' becomes 'sue' (both can mean to appeal or ask for something).
'on' says to put letters next to each other.
'case of' means to remove the middle letters (outsides of).
'extradition' with its centre removed is 'en'.
'sue' after 'en' is 'ENSUE'.
(Other definitions for ensue that I've seen before include "Turn out" , "Befall" , "Come to pass" , "Happen - to come later" , "Transpire" .)