Capital containing a hospital for outcasts (7)
I believe the answer is:
pariahs
'for outcasts' is the definition.
('pariah' can be a synonym of 'outcast')
'capital containing a hospital' is the wordplay.
'capital' becomes 'Paris' (Paris is the capital of France).
'containing' indicates putting letters inside.
'hospital' becomes 'H' (abbreviation for hospital).
'a'+'h'='ah'
'paris' enclosing 'ah' is 'PARIAHS'.
(Other definitions for pariahs that I've seen before include "Social outcasts" , "People one wouldn't associate with" .)