Buried in South Africa, bird bones (6)
I believe the answer is:
sterna
'bones' is the definition.
(more than one sternum)
'buried in south africa bird' is the wordplay.
'buried in' means one lot of letters goes inside another (inserted letters get buried).
'south africa' becomes 'sa' (abbreviation).
'bird' becomes 'tern' (tern is a kind of bird).
'sa' placed around 'tern' is 'STERNA'.
(Other definitions for sterna that I've seen before include "Breastbones" , "Bones in front" , "Formal backbones, Latin plural" .)