Miserable girl in police vehicle (5,5)
I believe the answer is:
black maria
'police vehicle' is the definition.
(informal term for a vehicle transporting prisoners)
'miserable girl' is the wordplay.
'miserable' becomes 'black' (black can mean miserable or unhappy).
'girl' becomes 'maria' ().
'black'+'maria'='BLACK MARIA'
'in' acts as a link.
(Other definitions for black maria that I've seen before include "vehicle for criminals" , "Old police van for transporting prisoners" , "Van with criminals" , "Police prisoners' transport" , "Nick vehicle" .)