Subdued when mated, maybe (5)
I believe the answer is:
tamed
'subdued' is the definition.
('tame' can be a synonym of 'subdue')
'mated maybe' is the wordplay.
'maybe' is an anagram indicator.
'mated' is an anagram of 'TAMED'.
'when' is the link.
(Other definitions for tamed that I've seen before include "Domesticated or subdued" , "Of animals, domesticated" , "Reined" , "now behaving himself?" .)