Regretted involving Government after American put the case (6)
I believe the answer is:
argued
'regretted involving government after american put the case' is the definition.
I can't judge whether this defines the answer.
'regretted involving government after american' is the wordplay.
'regretted' becomes 'rued' ('rue' can be a synonym of 'regret').
'involving' is an insertion indicator.
'government' becomes 'g' (abbreviation for government).
'after' says to put letters next to each other.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'rued' going around 'g' is 'rgued'.
'rgued' put after 'a' is 'ARGUED'.
Can you help me to learn more?
(Other definitions for argued that I've seen before include "Sought to show by reasoning" , "Bickered" , "Rag due (anag.)" , "Wrangled" , "Contended or debated" .)