Male seclusion could become mixed (13)
I believe the answer is:
miscellaneous
'mixed' is the definition.
('miscellaneous' can be a synonym of 'mixed')
'male seclusion could become' is the wordplay.
'could become' indicates an anagram.
'male'+'seclusion'='maleseclusion'
'maleseclusion' is an anagram of 'MISCELLANEOUS'.
(Other definitions for miscellaneous that I've seen before include "Of various types" , "Mixed, varied" , "Sundry" , "Consisting of several kinds" , "Assorted" .)