Subdued, one learned (8)
I believe the answer is:
mastered
'subdued' is the definition.
('master' can be a synonym of 'subdue')
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for mastered that I've seen before include "Red meats (anag.)" , "Streamed to be conquered" , "Overcame, difficulty or subject" , "Brought under control, overcame" .)
