Quiet partner is not giving up pouring oil on troubled waters (12)
I believe the answer is:
peacekeeping
'pouring oil on troubled waters' is the definition.
The definition suggests a present participle verb which matches the answer.
'quiet partner is not giving up' is the wordplay.
'quiet partner' becomes 'peace' (I've seen this in another clue).
'is not giving up' becomes 'keeping' (I can't explain this - if you can you should believe this answer much more).
'peace'+'keeping'='PEACEKEEPING'
Can you help me to learn more?
(Another definition for peacekeeping that I've seen is " The Blue Berets' remit".)