In Africa very deep chamber (4)
I believe the answer is:
cave
'chamber' is the definition.
(I have seen 'Underground chamber' mean 'cave' so perhaps 'chamber' could also mean 'cave')
'in africa very deep' is the wordplay.
'in' indicates the answer is hidden within the clue.
'CAVE' is hidden in the letters of 'africa very deep'.
(Other definitions for cave that I've seen before include "part of rocky coastline?" , "Beware" , "Troglodyte's home" , "Warning - grotto" , "Underground enclosure with surface access" .)