Entomb in hinterlands (5)
I believe the answer is:
inter
'entomb' is the definition.
('inter' can be a synonym of 'entomb')
'in hinterlands' is the wordplay.
'in' says the answer is hidden in the clue.
'INTER' is hidden in the letters of 'hinterlands'.
(Other definitions for inter that I've seen before include "Put underground" , "foreign team" , "Entomb" , "Settle in ground" , "Put into the ground" .)