Relative turned up in Greece inexplicably (5)
I believe the answer is:
niece
'relative' is the definition.
(type of relative)
'turned up in greece inexplicably' is the wordplay.
'turned up' says the letters should be written in reverse.
'in' indicates a hidden word.
'ecein' is hidden within 'greece inexplicably'.
'ecein' back-to-front is 'NIECE'.
(Other definitions for niece that I've seen before include "Brother's girl" , "Preparation for curdling milk" , "A sibling's child" , "member of different generation" , "Brother's daughter" .)