Relative in Greece injured back (5)
I believe the answer is:
niece
'relative' is the definition.
(niece is a kind of relative)
'in greece injured back' is the wordplay.
'in' indicates a hidden word.
'back' shows that the letters should be reversed in order.
'ecein' can be found hidden inside 'greece injured'.
'ecein' backwards is 'NIECE'.
(Other definitions for niece that I've seen before include "girl further down the line" , "Kinswoman" , "One of the family" , "Brother's girl" , "Family relation" .)