Convict fashionable couple (6)
I believe the answer is:
Here is my best explanation:
'convict' is the definition.
('inmate' can be a synonym of 'convict')
'fashionable couple' is the subsidiary indication.
'fashionable' becomes 'in' ('in' can be similar in meaning to 'fashionable').
'couple' becomes 'mate' ('mate' can be a synonym of 'couple'**).
(Other definitions for inmate that I've seen before include "Con", "One institutionally confined", "Someone confined, eg to hospital or prison", "eg Prisoner", "One is confined to an institution", "Lag", "Inhabitant of prison or hospital", "Person serving a jail sentence", "con" and "Inhabitant of prison or other institution".)